Even if this isn't a joke and Piratebay somehow manages to acquire Sealand, unless they can get another nation to formally acknowledge them, it won't mean a thing (it currently isn't recognized by anyone for those wondering). Plus, it would be incredibly easy for England to just just off Sealands connection to the inter-web thus making any hosting out of the question.
Edit: Oh, and it looks like Sealand isn't being put up for sale. According to the Evening Star, "It has been ruled for the past four decades by Major Roy Bates, now 85, and his family but they are looking to “transfer” tenancy to someone else, although they would still keep ownership." Heres the link to the source for your viewing pleasure.
http://www.eveningstar.co.uk/search/...ategory=search
Jam it back in, in the dark.