Regarding your example, you're asking the wrong question. That's not a Ponzi scheme because it makes it clear what kind of returns to expect and that the returns simply come from other investors. A Ponzi scheme involves persuading investors to invest (and reinvest the returns) on a fraudulent basis.

What Charles Ponzi did, and what has come to characterize Ponzi schemes today, is fraud. He made investors think that they were investing in something tradable (stamp coupons) when he actually only ever paid the returns using other investors' money, and it was able to go on for so long because most people simply reinvested their returns on the basis that they thought it was a sustainable investment.

This dynamic doesn't exist without fraud. No one is going to invest in ponzischeme.io on any other basis than exactly what it is, betting to get in early and to cash in their returns before everyone else does.

That said, if I was the world dictator, the ponzischeme.io guys would be in a labor camp, where they would be forced to do meaningful work.