I really don't understand what the author is trying to prove here. Countless sites let people upload and share free-form information (a few that come to mind: Dropbox, Gmail, Facebook) in ways that would be much easier for pirates to use than Twitter, and none of them are going to get shut down any time soon.

Yes, shutting down Megaupload and its kin isn't going to stop piracy. But I don't think that was ever the goal. As long as it reduces piracy by some measurable amount, which I think it will, then the censors will have succeeded.