For the British case, I believe the US is attempting to assert the fact that the kid in question was violating copyright law in the US, but with the various treaties in stuff in place, it might well mean that the US actually has a legitimate case for extradition. The copyrights in question are valid in Britain as well. Now as for the linking, it doesn't necessarily violate British law simply linking to copyrighted material, however it does violate US law.
In general a sticky case as they are US copyrights which are also respected/observed/copyrighted under British law, but the manner in which they were violated isn't necessarily illegal in Britain, but international treaties, etc might well mean that the British should be respecting US law in this case and grant the extradition.
I am not saying he should be extradited, but it is a lot more complicated then simply saying, "He can't be violating US law from England and what he is doing there isn't illegal". International treaties can be tricky things.
For Megaupload. Well, they certainly complied with most of the safe harbor provisions of DMCA, but they can't really claim to be a truely legitimate business as their primary method of income was related to/because of copyright infringement even if they weren't directly violating copyrights and were pretty quick about take-downs. It would be a little like saying a smuggler is really great at turning over their illegal goods when the coast guard catches up to them and claiming they had no idea what it was that they were carrying on behalf of their clients, but that they sure wouldn't want to participate in anything illegal, so here are the goods!
To me the case with Megaupload is a good example of why we DO NOT need anything resembling SOPA/PIPA. Feds can and have taken action against a pretty blatant copyright infringer, even if they were only facilitating copyright infringement indirectly (totally unbeknownst to them of course
).
As an example of how SOPA/PIPA likely would be abused to the n-th degree. Google the youtube vs viacom case that occured not too long ago. The judge threw the case out (Viacom was suing youtube as violating the DMCA) when it turned out that Viacom employees were INTENTIONALLY and anonimously uploading Viacom copyrighted materials to youtube, and then turning around issuing take down notices and malarky like that expressly to build a case that youtube was violating safe harbor provisions so that they could sue them.
Yeah, like SOPA and PIPA would never be abused (crap, DMCA is abused constantly by the big media companies).