I recently read about Richard O'Dwyer's case after following up on a 9gag post. Although he did not violate British laws, he still faces extradition to the United States because of a crazy extradition treaty. He is being extradited for things (posting links to pirated films and tv programmes on his website, TVShack) he did in Britain (he's British, by the way.) , that violated no British laws, that the United States government considers a crime.
How could the US do this? It turns out that during the Bush-Blair honeymoon, an extradition treaty was passed that allowed violators of certain US laws ---even if the violator was offshore!--- to be extradited to the US. I think a similar treaty with New Zealand was used for the arrest of Megaupload founder Kim Dotcom, a Finnish and German citizen, in New Zealand.
What's really grating about the Dwyer case is the one-sidedness of the treaty. Although the US can get British citizens extradited for violations of US law committed in Britain, the converse does not seem to apply. This is particularly worrying, since it means that even though your representatives (Parliament or Congress) do not deem certain acts to be illegal, you can still be on the hook for violating US laws on your own native soil.
I think it's a crazy situation: not only do you have to pay attention to the laws of your own country, you'll also have to pay attention to laws made by stupid US congressmen, thus making your own native soil effectively a neo-US colony.