"In the theories I work with, there is always an equilibrium where no one chooses to hold the currency, and its value falls to zero. In this sense, currencies are “fragile". (…) In the 1830s, 90% of the U.S. money supply was privately issued banknotes."
"...more than 2'600 cryptocurrencies have been launched. Nearly all of these remain today at the "zero value" equilibrium mentioned above."