Sealand is nothing more than a platform of concrete and steel that was created about 6 miles off the coast or England. It was constructed during World War 2 and was to be used as an anti-aircraft platform, but was later abandoned.
In 1967 a private group moved there and established it as its own sovereign nation. It now offers the most secure managed servers in the world and supposedly non-traceable network services.
Technically being a country, the servers are protected from other government subpoenas. Obviously a perfect place to conduct illegal activities, but I would assume other governments could place pressure on Sealand if its services were missed used.