What am I missing, why would it ever be good to invest in a ponzi?
It is good if you invest and people invest after you so you get paid :
Look at those 2ponzis :
1-https://bitcointalk.org/index.php?topic=472621.0
The address of deposit for round 1 was : 1F8ZKpjMDpnpF79mZ1pxZRoNKZgXm4Tf1d
You can see that everyone who invested between 18-02 when it started and approximatively 23-02 got 120% back, we are talking about 360BTC of deposits, everyone who deposited after 23-02 lost its investment, probably half the people who invested after 23-02 are people who invested before 23-02 as well but some people invested early and stopped investing in time so they made a lot of money, one of the player invested 64BTC and got 13BTC in profit
2-https://bitcointalk.org/index.php?topic=474730.0
Address of deposit 1NcHirWVDfUAngWLjBzmPCQaeZaMPCceHC It is a bit more complicated because there has been 2rounds on the same address but the principle is the same : people who invested early made money
Round3 may start tonight (chrono on the website ponzicoin.co), when it start we will have tens of btc of deposits so it is "safe" to deposit when the round starts
The ponzi owner is buying adds on bitcointalk (
https://bitcointalk.org/index.php?topic=482060.msg5301372#msg5301372), if its bid is accepted we would have hundreds of btc of deposits