So the basic formula appears to be this – the US Government felt the sites in question were illegal and since they were accessible from the US, they should do something about them. On its part, ICANN has no problem cooperating with the Government and is happy to act on terms of use violations either by domain owners or domain registrars.
That's quite disturbing.
(source: http://torrentfreak.com/pirate-bay-and-megaupload-escape-dom...)