Music Genome Project - Pandora

How do you find music given what you already know you like? A lot of web sites at the moment are leveraging the concept of 'tagging' i.e. if i like A, B, C and D and 50 other people also like A, B, C and D and 25 of them also like E who you've never heard of, there's a good chance you'll like E as well. Iterate the algorithm a few times and you'd get some good results.
These guys at Pandora, are trying to analyse the music styles themselves. You give feedback straight into the Java applet that loads on your screen. I have no idea how they deal with the copyright issues, but i like their style.
You can register for free and suffer ads or pay a subscription. Any songs you like, you can save the title and buy the album straight from the website via amazon or the song from iTunes (assuming unlike me, the British banking system doesn't treat you like a homicidal terrorist for wanting a credit card).
I think i'm gonna head home and run it for the night...