Some weeks ago I featured here the German company 4FriendsOnly.com that promotes a new way to sell music. 4FriendsOnly assume that users won't leave the p2p exchanges soon and that digital music will become ubiquitous. In this strategy paper (German only, pdf) they outline their concept. Basically every piece of music will get a unique ID or watermark. This "Audio-ID" sticks to the file whatever happens. In order to convince consumers to pay for something that they already have, 4FriendsOnly proposes community services (such as profiling and sharing of same music tastes). If this is enough to make users pay the 0.99 cents, I doubt. However the whole concept is a creative one and should be watched.