Interesting. Pandora is another music recommendation service (does music streaming for subscribers). They have a parameter-based approach – they call it the musical genome – in that they split apart the attributes of an artist along defined axes (The Cure, for example, is "electro, post-punk, melody-led etc"), unlike Last.fm, which seems to be more about plain old correlation coefficients. Also, less social and more straight-ahead commercial. US-centric, which kills the idea of giving them money for now. Though generally pretty nice.
First seen on Vanillasky.