The only legitimate ponzi there has been is WeeklyPonzi and 24HourPonzi, owned by the same guy.
I believe they're making a return at the end of the year or start or next year according to the site:
http://24hourponzi.com/You haven't tried ours! And yes weekly/24hour did scam people by running off with 5btc. Try some searching, you'll see the evidence.
Why We Created 'Yet Another Ponzi Site'
This site is a reaction to the poor quality of weeklyponzi.com and 24hourponzi.com and a few others, which we thought had some great features, but they had some very unfair and greedy practices. These are the main issues we had with the sites listed above:
Entries paid out of sequence
Over / under / early entries taken as a “donation”
Spending unconfirmed inputs, causing double spends
Ignoring any communication (emails / tweets / forum posts)
Crashing when blockchain.info goes down
Using a countdown timer which was reliant on each user's computer time
Ads
Taking the fee from user payout instead of user entry
"End of Round" funds taken as profit
No escrow
All of these failures have been addressed in this site code.
