In September 2015, the establishment of the peer-reviewed academic journal Ledger (ISSN 2379-5980) was announced. It covers studies of cryptocurrencies and related technologies, and is published by the University of Pittsburgh.[239] The journal encourages authors to digitally sign a file hash of submitted papers, which will then be timestamped into the bitcoin blockchain. Authors are also asked to include a personal bitcoin address in the first page of their papers.[240][241]
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.

That low point in unique addresses is a point where Bitcoin was hovering around $6,900 USD back around April 11, 2018. Using the seven-day average of the number of unique addresses (which smoothes out low points caused by low volume on the weekends), you can see that growth has returned since April to this underlying fundamental. The price today is lower, but the number of users appears to be growing again, and this time the network can support more transactions than before due to the rise of Segwit Adoption. If I had to guess I would say Bitcoin could now handle 50% to 100% more transactions per second than when we had the last peak in December/January.

According to The New York Times, libertarians and anarchists were attracted to the idea. Early bitcoin supporter Roger Ver said: "At first, almost everyone who got involved did so for philosophical reasons. We saw bitcoin as a great idea, as a way to separate money from the state."[119] The Economist describes bitcoin as "a techno-anarchist project to create an online version of cash, a way for people to transact without the possibility of interference from malicious governments or banks".[122]
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]

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]

There are many Bitcoin supporters who believe that digital currency is the future. Those who endorse it are of the view that it facilitates a much faster, no-fee payment system for transactions across the globe. Although it is not itself any backed by any government or central bank, bitcoin can be exchanged for traditional currencies; in fact, its exchange rate against the dollar attracts potential investors and traders interested in currency plays. Indeed, one of the primary reasons for the growth of digital currencies like Bitcoin is that they can act as an alternative to national fiat money and traditional commodities like gold.
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
Investigations into the real identity of Satoshi Nakamoto were attempted by The New Yorker and Fast Company. The New Yorker's investigation brought up at least two possible candidates: Michael Clear and Vili Lehdonvirta. Fast Company's investigation brought up circumstantial evidence linking an encryption patent application filed by Neal King, Vladimir Oksman and Charles Bry on 15 August 2008, and the domain name which was registered 72 hours later. The patent application (#20100042841) contained networking and encryption technologies similar to bitcoin's, and textual analysis revealed that the phrase "... computationally impractical to reverse" appeared in both the patent application and bitcoin's whitepaper.[11] All three inventors explicitly denied being Satoshi Nakamoto.[31][32]
Stefan Thomas, a Swiss coder and active community member, graphed the time stamps for each of Nakamoto's 500-plus bitcoin forum posts; the resulting chart showed a steep decline to almost no posts between the hours of 5 a.m. and 11 a.m. Greenwich Mean Time. Because this pattern held true even on Saturdays and Sundays, it suggested that Nakamoto was asleep at this time, and the hours of 5 a.m. to 11 a.m. GMT are midnight to 6 a.m. Eastern Standard Time (North American Eastern Standard Time). Other clues suggested that Nakamoto was British: A newspaper headline he had encoded in the genesis block came from the UK-published newspaper The Times, and both his forum posts and his comments in the bitcoin source code used British English spellings, such as "optimise" and "colour".[12]
Bitcoin has been criticized for the amount of electricity consumed by mining. As of 2015, The Economist estimated that even if all miners used modern facilities, the combined electricity consumption would be 166.7 megawatts (1.46 terawatt-hours per year).[129] At the end of 2017, the global bitcoin mining activity was estimated to consume between one and four gigawatts of electricity.[202] Politico noted that the even high-end estimates of bitcoin's total consumption levels amount to only about 6% of the total power consumed by the global banking sector, and even if bitcoin's consumption levels increased 100 fold from today's levels, bitcoin's consumption would still only amount to about 2% of global power consumption.[203]
In May 2013, Ted Nelson speculated that Japanese mathematician Shinichi Mochizuki is Satoshi Nakamoto.[33] Later in 2013 the Israeli researchers Dorit Ron and Adi Shamir pointed to Silk Road-linked Ross William Ulbricht as the possible person behind the cover. The two researchers based their suspicion on an analysis of the network of bitcoin transactions.[34] These allegations were contested[35] and Ron and Shamir later retracted their claim.[36]
^ 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.