Well, I think it is around for some time, but just today I had a look at Pandora site.
I have to admit that I started to really believe in music genoma!! It really exists! Each new music Pandora presented to my ears was 90% close to what I like. :) I don't say 100% because there were some bad choices. But for sure this is just a matter of time and fine tunning. I just listened to 8 songs.
Pandora is really an excellent way of getting personal playlists.
If you don't know it yet, give it a try: www.pandora.com