It's a huge step forward for Last.fm:
Audio Fingerprinting for Clean Metadata
Soon Last.fm will stop recommending Roberta Sa because I've listened to Roberta Sá. And once Last.fm's catalog is cleaned up, all Last.fm users will be able to use our massive meta data catalog to fix and extend the tags of their own MP3 collections. Furthermore, the quality of recommendations, neighbors, the radio stations, and just everything should gradually improve as a nice side effect of this major clean up.
Btw, the fingerprint extraction code is open source :-)