This company is doing some realy smart stuff on music intelligence. the principe is similar to the Amazon feature that tells you what other books people bought but it is so much cleverer. MusicGenome has a shed load of IPR relating to music algorithms and the mathematical structure of music. they are working on a mobile app (symbian/smartphone/java) that will ask you if you like a couple of music samples and based on your response, it can suggest (with staggering accuracy) other pieces you may like. You can then download, buy, listen etc. I tried a demo and was loving it.
Presumably the same science is equally applicable to other content (ringtones, films, games etc)
(Apple would love to get their hands on this for the next generation of "intelligent" iPods)