Hi,

This is an example of "legit" ponzi scheme :

http://ponzi.io/

You send money, and you get 120% back when someone send money after you.

It is a pyramidal system where you always get more money as long as people continue to send money.

I found it interesting because it makes you understand how a simple ponzi work.

The big difference with usual ponzi is that everything is transparent because you can check the blockchain yourself.

Of course don't invest money that you can't afford to loose.