I think in hindsight it was an obvious ponzi and I don't know how it was possible that it grew to such proportions.
...
Hindsight?!
It was obvious to probably the majority of people that it was a Ponzi from day-1. 7% weekly is obviously mathematically unsustainable. Plenty of people made this point over and over. The reality is that many of the "investors" knew it had to be a Ponzi, or highly suspected as much, and put money in anyway because they figured they could get out earlier than the next guy.
...
When the promised reward is high enough, people's emotions tend to override logical thought. So many people willingly accept almost any explanation for the exceptionally high reward because they want it to be true.
While it does not shift away the responsibility from the ponzi "investors", this emotional interface is exploited by a great number of ponzi schemes.
A gambling addict often can understand the irrationality of his behavior, but when confronted with a high potential reward his logic processor is deactivated by the positive emotionality of the possible future reward.
ya.ya.yo!