From an interview with Nicholas Weaver of UC Berkeley and the International Computer Science Institute:

Weaver:
You hear about people making money in Bitcoin or cryptocurrency. They only make money because some other sucker lost more. This is very different from the stock market.

I’m a savvy investor, and by “savvy investor,” I mean I put my money into index funds and ignore it for several years. During that time, there are dividends and share buybacks where the companies put their profits into me. I then eventually sell it to somebody else. And my gain is not just the difference between what I bought it for and what somebody else bought it for, but that plus the benefit of all the dividends and interest.

So the stock market and the bond market are a positive-sum game. There are more winners than losers. Cryptocurrency starts with zero-sum. So it starts with a world where there can be no more winning than losing. We have systems like this. It’s called the horse track. It’s called the casino. Cryptocurrency investing is really provably gambling in an economic sense. And then there’s designs where those power bills have to get paid somewhere. So instead of zero-sum, it becomes deeply negative-sum.

Effectively, then, the economic analogies are gambling and a Ponzi scheme. Because the profits that are given to the early investors are literally taken from the later investors. This is why I call the space overall, a “self-assembled” Ponzi scheme. There’s been no intent to make a Ponzi scheme. But due to its nature, that is the only thing it can be.