Right. Well, I don't actually buy mp3s from Amazon any more, preferring cd or better resolution. But I do like the principle that having bought a record, you can download it again if your drive blows up. Amazon applies the same reasoning to Kindle books - you don't need to back them up, just download again if your copy gets lost. It's a good idea because otherwise we all end up spending way too much time curating our collections and keeping them stable (!).