Q. If virtual currencies aren't backed by anything real, gold or some other physical commodity, does that mean they all eventually will be worthless?
A. You're right that they are not backed by a physical commodity, but then neither is the dollar and most other modern currencies. It’s long been known that currencies that are intrinsically worthless, mere pieces of paper, are recognized as valuable because payments with money are so much easier than the alternative, barter. The problem with barter, when everyone trades goods and services directly, is the dreaded “double coincidence of wants.” If I want to have dinner at my favorite restaurant but the cook is not interested in trading a meal for a bitcoin lecture, I have to keeping searching until I find a restaurant that I like where, coincidentally, the cook can’t hear enough about bitcoin.
Money, even intrinsically worthless paper money, cuts the “double coincidence” problem in half. I just need to find someone willing to pay me some of that paper for my lecture, then use that paper to pay for dinner. As long as I trust that someone will accept the paper, I’m willing to accept it in exchange for my lecture. It’s trust that the “worthless” piece of paper is actually worth something to other people that makes it an acceptable medium of exchange.
What was most interesting, however, was the Fed's observation under what conditions cryptos could not only match, but supplant fiat as the dominant currency. The answer: bitcoin would dominate payment methods in a dystopian world, in other words a "decentralized" world, in which there is no more faith - or trust - in central banks.
Which, of course, is the whole point behind cryptocurrencies in the first place: to replace the dollar, and other fiat currencies, once the entire fractional-reserve lending platform, and last 100 years of monetary philosophy are exposed to be a fraud.
"Lunacy" you say? Well, it's a conversation worth having after the next market crash, one which most likely will wipe out what little faith remains in central banks, in fractional reserve lending, in conventional economics and in fiat.