The Michigan Law Review has a piece on the Harry Potter novels and how they promote a libertarian agenda. While the author focus on Half-blood Prince I think The Order of the Phoenix with its depiction of Dolores Umbridge as a cruel uncaring bureaucrat is a much better illustration to kids of the dangers of unaccountable government bureaucracy.

http://papers.ssrn.com/sol3/papers.cfm?abstract_id=830765