"Here's a preliminary data mining analysis of musical social networking service Last.fm. An automated classification into clusters or sub populations with related musical genres reveals the structure of musical preferences among the users in a relatively large sample population. Musical tag clouds are adopted to characterise users and populations, which adds a highly descriptive value and aids with the interpretation of the results."
M. Hearst, and J. Pedersen. SIGIR '96: Proceedings of the 19th annual international ACM SIGIR conference on Research and development in information retrieval, page 76--84. New York, NY, USA, ACM, (1996)