Treasury secretary Janet Yellen likewise asserted that the "reality" of cryptocurrencies is that they "have been used to launder the profits of online drug traffickers; they've been a tool to finance terrorism."

Thus far, Bitcoin's supporters remain undeterred. (The term "Bitcoin" with a capital "B" is used here and throughout to refer to the system of cryptography and technology that produces the currency "bitcoin" with a lowercase "b" and verifies bitcoin transactions.) A survey of 3,000 adults in the fall of 2020 found that while only 4% of adults over age 55 own cryptocurrencies, slightly more than one-third of those aged 35-44 do, as do two-fifths of those aged 25-34. As of mid-2021, Coinbase?—?the largest cryptocurrency exchange in the United States?—?had 68 million verified users.

To younger Americans, digital money is as intuitive as digital media and digital friendships. But Millennials with smartphones are not the only people interested in bitcoin; a growing number of investors are also flocking to the currency's banner. Surveys indicate that as many as 21% of U.S. hedge funds now own bitcoin in some form. In 2020, after considering various asset classes like stocks, bonds, gold, and foreign currencies, celebrated hedge-fund manager Paul Tudor Jones asked, "[w]hat will be the winner in ten years' time?" His answer: "My bet is it will be bitcoin."