Actually, the only reason its legal to share books and not move/music/ect files is because the government said so. Nobody is encouraging nobody to break the law here, we are just stating our own opinion (free speech). I also want to note that it really dosent matter wether you keep the file or not, because nobody watches a movie more then once or twice. Nobody. As far as music goes, I believe here you need to be fair. If an artist just came out with an album, it would technichally be stealing if you download his songs for free, but if say, a year or two pass, and the musician dosent rely anymore on his record sales then it`s all good-my opinion.
Just like the Library. If a writer comes with a new book, hes expecting it to sell, I dont think the Library will offer his new book for us to loan and then return it (with no charge) but as time passes you can expect it will end up on their collection-for free.