Sites that say the payment is guaranteed are lying but in general the Ponzi games are very fun and potentially rewarding.
It should be obvious that if you invest in the beginning you have a high chance of payback, and as time goes it decreases.
Personally I've earned a good amount and can say they usually work. Or rather some work and some are scam, that's why you should check and be careful.
That said, I'm not against a sub-forum for ponzis. I come only for them, I never tried the other games and don't care about them.