Was Megaupload registered in US, too? Otherwise I think they have a very bogus case of "jurisdiction".

Just having the data pass through US servers doesn't or shouldn't count, the way the Internet works, and how it's supposed to decentralize the data to keep it more localized. Otherwise you could argue that just by the nature of people using Megaupload from US would also give the US government the right to prosecute Megaupload. If that's the case, then Google could be prosecuted in countries where it doesn't have headquarters, too.