i read an article about this on the newspaper.
i thikn the main mission is to have people trade their CDs so they can be exposed to new music they want to try. you can create profiles so people can see what you listen to and be able to recommend you things. so then once you send off a CD to someone, you have to delete those songs off your harddrive, because of the whole piracy thing. once you send it off to trade with someone, it's technically not yours anymore, so those songs shouldn't be on your harddrive either.
i guess their philosophy is good in that it considers the artist, but honestly, i don't think people will delete their stuff, so i don't really know how it works yet. i guess theoretically it sounds like a good way to discover new music through other people ;]