Grooveshark's beluga project ( http://beluga.grooveshark.com ) reveals a lot of the same patterns. Looking up Mormon tabernacle choir, for instance, shows a high listenership of politically active, religious conservatives, while people that listen to system of a down tend to be moderate liberals with less political involvement. Music demographics data is fascinating!
For example, Paul van Dyk, Three Drives, and Ferry Corsten all have "IT Specialist / Programmer" as highly over-represented (wow!).
In addition, Tiësto (had to look up Tiesto) shows that advertising does in fact, work! ... 92% of the listeners on Grooveshark uses Windows Live Spaces.
He was hired by Microsoft to sell Vista to the Dutch market: http://www.reuters.com/article/2007/04/15/music-tiesto-dc-id...
Good find! :)