I get my music recommendations from music blogs or my local record store, and I always always always find them more relevant than anything an algorithm poops out. Finding a way to scale that up would be interesting, but I also don't really think that there's a lot of money in it. Google could do this, really, or Facebook, I suppose, because they have the huge amount of activity data that could be used to take the place of "Hey, I like this Galactic Cannibal record, what else should I be listening to?"