I love watching ideas turn into reality. Mike, from www.FIQL.com, recently sent me this mail because comments were closed on the post in question:
Hey Josh, ran across an old post of yours here: http://blogs.msdn.com/jledgard/archive/2004/06/07/150302.aspx Thought you might be interested in a site we've built. FIQL.com. it's a site all about playlists and you can upload playlists that you've created on itunes as well as listen to other's people's playlists (Well at least samples). Anyway, check it out - i think it's a lot of what you were talking about. EXCEPT, that part about mapping. That wouldn't work so well on our site because people create playlists for the most interesting reasons. Some people have a playlist all about snow or some other whacky theme. So a similar mapping may not necessarily indicate similar taste. Anyway we're exploring the whole recommendation thing but right now it seems human recommendations work better on our site. Would love to get your take.
Here is my take: