Recall that unique addresses are a proxy for the number of users, because they indicate how many non-zero Bitcoin addresses are in use. This metric has its strengths and weaknesses, which I wrote about here. Also, I have reviewed several other pricing methods which attempt to do the same thing using Metcalfe's Law. You can find those here and here.
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."[60][61]
Nigel Dodd argues in The Social Life of Bitcoin that the essence of the bitcoin ideology is to remove money from social, as well as governmental, control.[124] Dodd quotes a YouTube video, with Roger Ver, Jeff Berwick, Charlie Shrem, Andreas Antonopoulos, Gavin Wood, Trace Meyer and other proponents of bitcoin reading The Declaration of Bitcoin's Independence. The declaration includes a message of crypto-anarchism with the words: "Bitcoin is inherently anti-establishment, anti-system, and anti-state. Bitcoin undermines governments and disrupts institutions because bitcoin is fundamentally humanitarian."[124][123]

The very first major jump in Bitcoin price took place in July 2010. At this point, the value of Bitcoin went from about $0.0008 all the way up to $0.08, a truly dramatic increase in price. At this point and in the following year, very few exchanges supported trading of Bitcoin. There was also extremely limited liquidity at this time due to cryptocurrency still being relatively unknown. That meant that when the price started an increase in June 2011 from about $0.95, the approach was among the steepest recorded. Unfortunately, the drop also followed suit. By mid-June of that year, Bitcoin was up to $320, an all-time high. By November, it had declined 94 percent all the way to $20.
Illiquidity. This is mostly moot due to Bitcoin’s $47 market cap but it still makes users sweat. It’s highly unlikely that Bitcoin’s price would plummet and you’d be unable to take action, but it’s still unsettling.  As more investors invest, however, illiquidity becomes a negligible risk, as there will likely always be a buyer for Bitcoins waiting.
Because of bitcoin's decentralized nature and its trading on online exchanges located in many countries, regulation of bitcoin has been difficult. However, the use of bitcoin can be criminalized, and shutting down exchanges and the peer-to-peer economy in a given country would constitute a de facto ban.[164] The legal status of bitcoin varies substantially from country to country and is still undefined or changing in many of them. Regulations and bans that apply to bitcoin probably extend to similar cryptocurrency systems.[165]
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.
In October 2013, the FBI seized roughly 26,000 BTC from website Silk Road during the arrest of alleged owner Ross William Ulbricht.[78][79][80] Two companies, Robocoin and Bitcoiniacs launched the world's first bitcoin ATM on 29 October 2013 in Vancouver, BC, Canada, allowing clients to sell or purchase bitcoin currency at a downtown coffee shop.[81][82][83] Chinese internet giant Baidu had allowed clients of website security services to pay with bitcoins.[84]

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 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.
Wallets and similar software technically handle all bitcoins as equivalent, establishing the basic level of fungibility. Researchers have pointed out that the history of each bitcoin is registered and publicly available in the blockchain ledger, and that some users may refuse to accept bitcoins coming from controversial transactions, which would harm bitcoin's fungibility.[117]
Despite a fairly steep dropoff during early 2018, the average number of bitcoin transactions per block has steadily increased throughout the network’s history, from just 1 in 2010 to more than 1,800 today. Developers also predict that second-layer technologies such as the Lightning Network (LN) should allow the network to scale its transaction capacity exponentially while also making BTC useful for everyday payments and microtransactions.

Illiquidity. This is mostly moot due to Bitcoin’s $47 market cap but it still makes users sweat. It’s highly unlikely that Bitcoin’s price would plummet and you’d be unable to take action, but it’s still unsettling.  As more investors invest, however, illiquidity becomes a negligible risk, as there will likely always be a buyer for Bitcoins waiting.
"Satoshi Nakamoto" is presumed to be a pseudonym for the person or people who designed the original bitcoin protocol in 2008 and launched the network in 2009. Nakamoto was responsible for creating the majority of the official bitcoin software and was active in making modifications and posting technical information on the bitcoin forum.[12] There has been much speculation as to the identity of Satoshi Nakamoto with suspects including Dai, Szabo, and Finney – and accompanying denials.[28][29] The possibility that Satoshi Nakamoto was a computer collective in the European financial sector has also been discussed.[30]
If the private key is lost, the bitcoin network will not recognize any other evidence of ownership;[30] the coins are then unusable, and effectively lost. For example, in 2013 one user claimed to have lost 7,500 bitcoins, worth $7.5 million at the time, when he accidentally discarded a hard drive containing his private key.[74] A backup of his key(s) would have prevented this.

In June 2013, Bitcoin Foundation board member Jon Matonis wrote in Forbes that he received a warning letter from the California Department of Financial Institutions accusing the foundation of unlicensed money transmission. Matonis denied that the foundation is engaged in money transmission and said he viewed the case as "an opportunity to educate state regulators."[182]

The number of businesses accepting bitcoin continued to increase. In January 2017, NHK reported the number of online stores accepting bitcoin in Japan had increased 4.6 times over the past year.[123] BitPay CEO Stephen Pair declared the company's transaction rate grew 3× from January 2016 to February 2017, and explained usage of bitcoin is growing in B2B supply chain payments.[124]

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]
^ 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.