If any of the founders sold shares to US residents, then I believe SEC registration would have been required. How is this different than Satoshi Dice? But SEC registration most certainly did not happen (please correct me if I'm wrong), so I believe the SEC would have a case against any of the 47 initial founders should any of them financially profit by selling their stake to US residents.
EDIT: This is interesting. Perhaps the Eric Voorhees / Satoshi Dice precedent just killed the IPO model for launching cryptocurrencies.
It's one of the reasons I dropped the IPO model for MC2. I kind of wonder if it has ramifications for spinoffs too, because with a spinoff of Bitcoin you could buy bitcoins now and get coins for them later.
Someone at the company I work for is talking to some corporate lawyers right now about the legality of these IPOs in general.
Note that a lot of banking for other IPOs seems to be done offshore, too (not naming names), and that they're going so far as to avoid the term "IPO" lately.