When we talk about Bitcoin, Ethereum, or any other crypto currency, neither the "Ponzi" nor the "pyramid" are completely accurate descriptions of how these systems actually work. Traditional Ponzi schemes are usually managed by a central operator , who is responsible for attracting new funds and paying out a certain algorithm. Schemes collapse when the claims exceed the amount of funds deposited, so that the scheme operator can not satisfy investors' requests, causing a loss of confidence or a massive outflow that undermines the liquidity of the system.