Various journalists,[204][211] economists,[212][213] and the central bank of Estonia[214] have voiced concerns that bitcoin is a Ponzi scheme. In 2013, Eric Posner, a law professor at the University of Chicago, stated that "a real Ponzi scheme takes fraud; bitcoin, by contrast, seems more like a collective delusion."[215] A 2014 report by the World Bank concluded that bitcoin was not a deliberate Ponzi scheme.[216]:7 The Swiss Federal Council[217]:21 examined the concerns that bitcoin might be a pyramid scheme; it concluded that, "Since in the case of bitcoin the typical promises of profits are lacking, it cannot be assumed that bitcoin is a pyramid scheme." In July 2017, billionaire Howard Marks referred to bitcoin as a pyramid scheme.[218]

In July 2013, a project began in Kenya linking bitcoin with M-Pesa, a popular mobile payments system, in an experiment designed to spur innovative payments in Africa.[71] During the same month the Foreign Exchange Administration and Policy Department in Thailand stated that bitcoin lacks any legal framework and would therefore be illegal, which effectively banned trading on bitcoin exchanges in the country.[72][73] According to Vitalik Buterin, a writer for Bitcoin Magazine, "bitcoin's fate in Thailand may give the electronic currency more credibility in some circles", but he was concerned it didn't bode well for bitcoin in China.[74]
If fewer people begin to accept Bitcoin as a currency, these digital units may lose value and could become worthless. There is already plenty of competition, and though Bitcoin has a huge lead over the other 100-odd digital currencies that have sprung up, thanks to its brand recognition and venture capital money, a technological break-through in the form of a better virtual coin is always a threat.
Venture capitalists, such as Peter Thiel's Founders Fund, which invested US$3 million in BitPay, do not purchase bitcoins themselves, but instead fund bitcoin infrastructure that provides payment systems to merchants, exchanges, wallet services, etc.[150] In 2012, an incubator for bitcoin-focused start-ups was founded by Adam Draper, with financing help from his father, venture capitalist Tim Draper, one of the largest bitcoin holders after winning an auction of 30,000 bitcoins,[151] at the time called "mystery buyer".[152] The company's goal is to fund 100 bitcoin businesses within 2–3 years with $10,000 to $20,000 for a 6% stake.[151] Investors also invest in bitcoin mining.[153] According to a 2015 study by Paolo Tasca, bitcoin startups raised almost $1 billion in three years (Q1 2012 – Q1 2015).[154]
In 2014, researchers at the University of Kentucky found "robust evidence that computer programming enthusiasts and illegal activity drive interest in bitcoin, and find limited or no support for political and investment motives".[127] Australian researchers have estimated that 25% of all bitcoin users and 44% of all bitcoin transactions are associated with illegal activity as of April 2017. There were an estimated 24 million bitcoin users primarily using bitcoin for illegal activity. They held $8 billion worth of bitcoin, and made 36 million transactions valued at $72 billion.[227][228] A group of researches analyzed bitcoin transactions in 2016 and came to a conclusion that "some recent concerns regarding the use of bitcoin for illegal transactions at the present time might be overstated".[229]
Bitcoin is an increasingly popular cryptocurrency that utilizes blockchain technology to facilitate transactions. Basically, a user obtains a Bitcoin wallet that can be used for storing bitcoins and both sending and receiving of payments. The blockchain technology used by Bitcoin is really just a shared public ledger that is used by the entire public network. The technology used is secured through cryptography, a branch of mathematics that provides a highly secure means of facilitating and recording transactions on the network.

^ Jump up to: a b c d "Statement of Jennifer Shasky Calvery, Director Financial Crimes Enforcement Network United States Department of the Treasury Before the United States Senate Committee on Banking, Housing, and Urban Affairs Subcommittee on National Security and International Trade and Finance Subcommittee on Economic Policy" (PDF). Financial Crimes Enforcement Network. 19 November 2013. Archived (PDF) from the original on 9 October 2016. Retrieved 1 June 2014. 

On 6 August 2010, a major vulnerability in the bitcoin protocol was spotted. Transactions weren't properly verified before they were included in the transaction log or blockchain, which let users bypass bitcoin's economic restrictions and create an indefinite number of bitcoins.[25][26] On 15 August, the vulnerability was exploited; over 184 billion bitcoins were generated in a transaction, and sent to two addresses on the network. Within hours, the transaction was spotted and erased from the transaction log after the bug was fixed and the network forked to an updated version of the bitcoin protocol.[27] This was the only major security flaw found and exploited in bitcoin's history.[25][26]
In January 2012, bitcoin was featured as the main subject within a fictionalized trial on the CBS legal drama The Good Wife in the third-season episode "Bitcoin for Dummies". The host of CNBC's Mad Money, Jim Cramer, played himself in a courtroom scene where he testifies that he doesn't consider bitcoin a true currency, saying "There's no central bank to regulate it; it's digital and functions completely peer to peer".[49]
Every 2,016 blocks (approximately 14 days at roughly 10 min per block), the difficulty target is adjusted based on the network's recent performance, with the aim of keeping the average time between new blocks at ten minutes. In this way the system automatically adapts to the total amount of mining power on the network.[3]:ch. 8 Between 1 March 2014 and 1 March 2015, the average number of nonces miners had to try before creating a new block increased from 16.4 quintillion to 200.5 quintillion.[80]
Bitcoin's blockchain can be loaded with arbitrary data. In 2018 researchers from RWTH Aachen University and Goethe University identified 1,600 files added to the blockchain, 59 of which included links to unlawful images of child exploitation, politically sensitive content, or privacy violations. "Our analysis shows that certain content, eg, illegal pornography, can render the mere possession of a blockchain illegal."[229]
An official investigation into bitcoin traders was reported in May 2018.[175] The U.S. Justice Department launched an investigation into possible price manipulation, including the techniques of spoofing and wash trades.[176][177][178] Traders in the U.S., the U.K, South Korea, and possibly other countries are being investigated.[175] Brett Redfearn, head of the U.S. Securities and Exchange Commission's Division of Trading and Markets, had identified several manipulation techniques of concern in March 2018.
Most stock quote data provided by BATS. Market indices are shown in real time, except for the DJIA, which is delayed by two minutes. All times are ET. Disclaimer. Morningstar: © 2018 Morningstar, Inc. All Rights Reserved. Factset: FactSet Research Systems Inc.2018. All rights reserved. Chicago Mercantile Association: Certain market data is the property of Chicago Mercantile Exchange Inc. and its licensors. All rights reserved. Dow Jones: The Dow Jones branded indices are proprietary to and are calculated, distributed and marketed by DJI Opco, a subsidiary of S&P Dow Jones Indices LLC and have been licensed for use to S&P Opco, LLC and CNN. Standard & Poor's and S&P are registered trademarks of Standard & Poor's Financial Services LLC and Dow Jones is a registered trademark of Dow Jones Trademark Holdings LLC. All content of the Dow Jones branded indices © S&P Dow Jones Indices LLC 2018 and/or its affiliates.
17-20 November 2017 $7,600-8,100 Briefly topped at USD $8004.59/BTC at 01:14:11 UTC before retreating from highs. At 05:35 UTC on 20 November 2017 it stood at USD$7,988.23/BTC according to CoinDesk.[165] This surge in bitcoin may be related to developments in the 2017 Zimbabwean coup d'état. The market reaction in one bitcoin exchange is alarming as 1 BTC topped nearly US$13,500, just shy of 2 times the value of the International market.[166][167]
“These companies are using extraordinary amounts of electricity – typically thousands of times more electricity than an average residential customer would use,” a spokesperson for the New York State Department of Public Service told Wired. “The sheer amount of electricity being used is leading to higher costs for customers in small communities because of a limited supply of low-cost hydropower.”
In December, 2013, Techcrunch published an interview with researcher Skye Grey who claimed textual analysis of published writings shows a link between Satoshi and bit-gold creator Nick Szabo. And perhaps most famously, in March 2014, Newsweek ran a cover article claiming that Satoshi is actually an individual named Satoshi Nakamoto – a 64-year-old Japanese-American engineer living in California. The list of suspects is long, and all the individuals deny being Satoshi.
According to the Library of Congress, an "absolute ban" on trading or using cryptocurrencies applies in eight countries: Algeria, Bolivia, Egypt, Iraq, Morocco, Nepal, Pakistan, and the United Arab Emirates. An "implicit ban" applies in another 15 countries, which include Bahrain, Bangladesh, China, Colombia, the Dominican Republic, Indonesia, Iran, Kuwait, Lesotho, Lithuania, Macau, Oman, Qatar, Saudi Arabia and Taiwan.[166]
To lower the costs, bitcoin miners have set up in places like Iceland where geothermal energy is cheap and cooling Arctic air is free.[204] Bitcoin miners are known to use hydroelectric power in Tibet, Quebec, Washington (state), and Austria to reduce electricity costs.[203][205][206][207] Miners are attracted to suppliers such as Hydro Quebec that have energy surpluses.[208] According to a University of Cambridge study, much of bitcoin mining is done in China, where electricity is subsidized by the government.[209][210]
Bitcoin mining operations take a lot of effort and power, and the sheer amount of competition makes it difficult for newcomers to enter the race and profit. A new miner would not only need to have adequate computing power and the knowledge to use it to outcompete the competition, but would also need the extensive amount of capital necessary to fund the operations.
Bitcoin is a new currency that was created in 2009 by an unknown person using the alias Satoshi Nakamoto. Transactions are made with no middle men – meaning, no banks! Bitcoin can be used to book hotels on Expedia, shop for furniture on Overstock and buy Xbox games. But much of the hype is about getting rich by trading it. The price of bitcoin skyrocketed into the thousands in 2017.

More recently, at a congressional hearing on Capitol Hill, global economist and New York University professor Nouriel Roubini said, "Crypto is the mother or father of all scams and bubbles." He called out "swindlers" who tapped into investors' fear of missing out and took them for a ride with "crappy assets that went into a bust and crash — in a matter of months — like you have not seen in any history of financial bubbles."

Bitcoin and other cryptocurrencies have been identified as economic bubbles by at least eight Nobel Memorial Prize in Economic Sciences laureates, including Robert Shiller,[191] Joseph Stiglitz,[192] and Richard Thaler.[193][13] Noted Keyensian economist Paul Krugman wrote in his New York Times column criticizing bitcoin, calling it a bubble and a fraud;[194] and professor Nouriel Roubini of New York University called bitcoin the "mother of all bubbles."[195] Central bankers, including former Federal Reserve Chairman Alan Greenspan,[196] investors such as Warren Buffett,[197][198] and George Soros[199] have stated similar views, as have business executives such as Jamie Dimon and Jack Ma.[200]
In January 2015 Coinbase raised 75 million USD as part of a Series C funding round, smashing the previous record for a bitcoin company.[109] Less than one year after the collapse of Mt. Gox, United Kingdom-based exchange Bitstamp announced that their exchange would be taken offline while they investigate a hack which resulted in about 19,000 bitcoins (equivalent to roughly US$5 million at that time) being stolen from their hot wallet.[110] The exchange remained offline for several days amid speculation that customers had lost their funds. Bitstamp resumed trading on 9 January after increasing security measures and assuring customers that their account balances would not be impacted.[111]

The Bank for International Settlements summarized several criticisms of bitcoin in Chapter V of their 2018 annual report. The criticisms include the lack of stability in bitcoin's price, the high energy consumption, high and variable transactions costs, the poor security and fraud at cryptocurrency exchanges, vulnerability to debasement (from forking), and the influence of miners.[187][188][189]
Josiah is an assistant editor at CCN. A former ancient and medieval literature teacher, he has been reporting on cryptocurrency since 2014. He lives in rural North Carolina with his wife and children. He holds investment positions in bitcoin and other large-cap cryptocurrencies. Follow him on Twitter @Y3llowb1ackbird or email him directly at josiah.wilmoth(at)
According to the European Central Bank, the decentralization of money offered by bitcoin has its theoretical roots in the Austrian school of economics, especially with Friedrich von Hayek in his book Denationalisation of Money: The Argument Refined,[120] in which he advocates a complete free market in the production, distribution and management of money to end the monopoly of central banks.[121]:22

On 6 August 2013, Federal Judge Amos Mazzant of the Eastern District of Texas of the Fifth Circuit ruled that bitcoins are "a currency or a form of money" (specifically securities as defined by Federal Securities Laws), and as such were subject to the court's jurisdiction,[75][76] and Germany's Finance Ministry subsumed bitcoins under the term "unit of account"—a financial instrument—though not as e-money or a functional currency, a classification nonetheless having legal and tax implications.[77]
“These companies are using extraordinary amounts of electricity – typically thousands of times more electricity than an average residential customer would use,” a spokesperson for the New York State Department of Public Service told Wired. “The sheer amount of electricity being used is leading to higher costs for customers in small communities because of a limited supply of low-cost hydropower.”
Computing power is often bundled together or "pooled" to reduce variance in miner income. Individual mining rigs often have to wait for long periods to confirm a block of transactions and receive payment. In a pool, all participating miners get paid every time a participating server solves a block. This payment depends on the amount of work an individual miner contributed to help find that block.[82]
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