The interesting thing about CC Mixter is that each remix links back to the songs it was derived from, so that you get a family tree of the remix space.
Victor points out tome that CC Mixter "is a great place for songwriters to get exposure to the remix community. As in: it's a good chance to have whole audiences hear their music even if it's not in a context they were originally thinking of."
Musicians can upload complete tracks or solo tracks (preferably a Capella) to encourage others to use their tracks.
Because of the two contests CC Mixter is running, samples from their tracks could (theoretically) end up on either the next Chuck D. record or the CC promo CD that will feature 12 cuts from CC Mixter.
Victor is gathering some loops/samples from the Magnatune archive and uploading them as Loop Libraries (zip), encouraging others to use our work.
Besides getting more publicity for our artists, remixes, when they get printed onto commercially-sold CDs, also generate commercial-use licensing revenue, so CC Mixter is a wonderful thing for Magnatune musicians.