Not sure why this was voted down.
You make a good point about the possibility of mining all this data, but I'm not sure I want to give it away. We (well, some of us), go to lengths to maintain separate online personas. Why do I care if Facebook knows what my most-played songs are? I can get that info from iTunes, etc.
They're going to need a strong pull (killer app, privacy controls, whatever) to get my data.