My feeling is the primary difference would have been that there would have been shareholders, apart from the legitimate users we hear about today, who would have been furious that their investment had been tampered with by the govt. So maybe in that sense it would have required the state to have a stronger case before taking action.

Not being an American I might have missed a huge example of the opposite, but I haven't seen the US gov shut down and destroy a public company. Sue them, yes, but destroy, no. So, presumably, had Megaupload gone public, my guess is that it would still exist, while being sued. It would still have resources to defend its self. What has happened here, or what was attempted here was the destruction of a business and the removal of its ability to fight back. I cant see that happening to a public company.

OK, Megaupload can be argued to be shady, but surely the action against is is equally shady.

Hate to be the bearer of bad news but public companies engaging in crime is not uncommon.