I'm just betting that the investors, who are pretty savvy, do know whether their financials are good.You should probably stay far away from Wall St for your own good. The savviness of the investors should be a warning sign, not one that instills trust. Remember, in an IPO, they are the ones on the other side of the handshake. They have every incentive to fool you.
As for your other points. A ponzi scheme is like Bernie Madoff where you pay off early investors with the money from later investors. I don't believe being open with how the money works would change that. Pyramids are usually where members are pressured to get even more members because a percentage of the new hires' sales goes to the person who brought them in. The bottom of the pyramid cannot get their investment back because they run out of "greater fools". It's all a bit confused because if you buy into Groupon you also get ownership of a business which may or may not be worth something.
We really can argue about the semantics of these labels but really what it comes down to for me are these two questions: Is this a healthy business, and have the founders acted in the best interest of the business? To me the answers are I don't think so and absolutely not. I don't trust an executive team that would allow 90% of a non-profitable company's runway to go into their own pocket with my money.
They've acted in their own self interest to which many would say "whatever, it was a fair trade". I want people the people who think that way to realize that sometimes we restrict trades that are "fair" regardless of how stupid you are for getting into them. Roulette is a losing game but it is a fair game. We also restrict and regulate it heavily.
Anyway, I think we're in agreement on this: it's really interesting to talk about. :-)