If it's greater fool plus no inherent value of the underlying then that's a Ponzi Scheme. You aren't buying anything, no revenue stream, no dividends, no assets, no cash, etc, just the hope you can sell to a greater fool. A Ponzi Scheme is the same thing - you can make money if and only if suckers keep putting money into the scheme (and you cash out at the right time).
Ponzi works like this: Say this big shot investor invites you into his fund that gives a great return of 16% compounded year over year. The investor encourages his investor to put in regular amounts over time. He's got a fancy website that tracks your account balance which of course is only a ledger he owns. No financial institution seems to carry any money. It is a confidence scam. As long as you are confident that your money is being increased regularly and you are waiting long into the future to take it out it is never discovered that the Ponzi scammer is stealing all the money and living an extravagant lifestyle.