@SteveR: to prevent hijacking you have to be the dominant distribution source of the file. That’s good because it gives labels an incentive to license.
Also, it’s an interesting incentive for them to push their licencees to support this whole mechanism, and as a result to help the mechanism get started. They should be adding contract clauses to require that they own the WOAF (or analogous) field.
@teru, man, you outclass me by a long shot. Thinking about the mixter case, it would be totally natural to have the cchost set the link to point to the song page there. The ccmixter song page could manage mixbacks, and listeners could follow from there to any page you want to set as your personal link.