If it's not a "known scam" then it's hard to say what should be done as they may not have had time to do their research. If it is a "known scam" then theoretically they could be liable as well. Then again, people should do their own research, so it's a muddy situation, especially if you're trying to keep regulatory bodies from getting involved.

Even CryptoKitties seemed to be a pyramid scheme of sorts. You constantly needed new people coming in to buy the kitties, but they were degrading into nothing as you used them. It was a brilliant scheme to get a lot of money from unwitting people, because most of that information (degrading of assets, fees for sale, fees to breed) were not disclosed anywhere.

The main lessons are "buyer beware" and "do your research."