It has been a year since I made this post, but I thought that it deserved a bump given the recent activity in the Bitcoin space.
It's a nice thread that will help people understand the definitions.
I'm not sure there is a big differences with ponzi and piramid scheme.
Both of them earn their rewards thanks to the newcomers.
Enlight me if I'm wrong but I think it's the same thing.
Ponzi scheme is an American thing. In Europe we don't use this name and instead use pyramid scheme and mlm to describe this. Ponzi scheme was repeated by another proud American Madoff who did the same thing. There were no levels in his system just him on top stealing from everyone and lying to everyone.