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.
Legal Gray Area. Major governments have largely remained on the sidelines, and this has created both a sense of potential and apprehension for Bitcoin proponents and critics respectively. Bitcoin isn’t backed by a regulatory agency and a government would technically be ceding power by supporting a decentralized currency. This has been largely officially unaddressed. Bitcoin’s price, however, tends to be very sensitive to any news concerning the US government’s opinion of cryptocurrencies. For example, when the SEC denied the approval of bitcoin-based exchange-traded-products—essentially bitcoin-backed assets on the stock market—in 2017, Bitcoin’s price dropped 18%. Yet while the price and adoption of Bitcoin would be affected by government action, governments are unable to criminalize Bitcoin. In fact, governments such as the United States and China have invested in it at some capacity.
The price of bitcoins has gone through cycles of appreciation and depreciation referred to by some as bubbles and busts. In 2011, the value of one bitcoin rapidly rose from about US$0.30 to US$32 before returning to US$2. In the latter half of 2012 and during the 2012–13 Cypriot financial crisis, the bitcoin price began to rise, reaching a high of US$266 on 10 April 2013, before crashing to around US$50. On 29 November 2013, the cost of one bitcoin rose to a peak of US$1,242. In 2014, the price fell sharply, and as of April remained depressed at little more than half 2013 prices. As of August 2014 it was under US$600. During their time as bitcoin developers, Gavin Andresen and Mike Hearn warned that bubbles may occur.
Regulatory Risk: Bitcoins are a rival to government currency and may be used for black market transactions, money laundering, illegal activities or tax evasion. As a result, governments may seek to regulate, restrict or ban the use and sale of bitcoins, and some already have. Others are coming up with various rules. For example, in 2015, the New York State Department of Financial Services finalized regulations that would require companies dealing with the buy, sell, transfer or storage of bitcoins to record the identity of customers, have a compliance officer and maintain capital reserves. The transactions worth $10,000 or more will have to be recorded and reported.
Additionally, FinCEN claimed regulation over American entities that manage bitcoins in a payment processor setting or as an exchanger: "In addition, a person is an exchanger and a money transmitter if the person accepts such de-centralized convertible virtual currency from one person and transmits it to another person as part of the acceptance and transfer of currency, funds, or other value that substitutes for currency."
Bitcoin is a peer-to-peer version of electronic cash that allows payments to be sent directly from one party to another without going through a financial institution. The network timestamps transactions by hashing them into an ongoing chain of hash-based proof-of-work, forming a record that cannot be changed without redoing the proof-of-work. – Satoshi Nakamoto
Prior to the release of bitcoin there were a number of digital cash technologies starting with the issuer based ecash protocols of David Chaum and Stefan Brands. Adam Back developed hashcash, a proof-of-work scheme for spam control. The first proposals for distributed digital scarcity based cryptocurrencies were Wei Dai's b-money and Nick Szabo's bit gold. Hal Finney developed reusable proof of work (RPOW) using hashcash as its proof of work algorithm.
In the early days, Nakamoto is estimated to have mined 1 million bitcoins. Before disappearing from any involvement in bitcoin, Nakamoto in a sense handed over the reins to developer Gavin Andresen, who then became the bitcoin lead developer at the Bitcoin Foundation, the 'anarchic' bitcoin community's closest thing to an official public face.
After a certain amount of transactions have been verified by a miner, they will receive newly minted bitcoins for their work and thus new bitcoins will be added into circulation, while the number of bitcoins in circulations are now in the multi-millions range, the maximum amount of bitcoins that can ever be created is capped at 21 million. The creation rate is automatically halved every few years as more bitcoins are added into circulation, whilst this system is modeled after gold, mining difficulty is always increasing and makes finding new bitcoins more rare as the number of available bitcoins reaches the 21 million cap.
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. 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. 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.
In January 2015 Coinbase raised 75 million USD as part of a Series C funding round, smashing the previous record for a bitcoin company. 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. 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.
Google Trends structures the chart to represent a relative search interest to the highest points in the chart. A value of 100 is the peak popularity for the term “Bitcoin” and a value of 50 means it was half as popular at that time. A score of 0 indicates that the term was less than 1% as popular as the peak. It’s amazing how the searches relating to Bitcoin have spiked in the past few years.
Bitcoin is pseudonymous, meaning that funds are not tied to real-world entities but rather bitcoin addresses. Owners of bitcoin addresses are not explicitly identified, but all transactions on the blockchain are public. In addition, transactions can be linked to individuals and companies through "idioms of use" (e.g., transactions that spend coins from multiple inputs indicate that the inputs may have a common owner) and corroborating public transaction data with known information on owners of certain addresses. Additionally, bitcoin exchanges, where bitcoins are traded for traditional currencies, may be required by law to collect personal information.