"Pull down the barriers! Share music with all your friends!"<p>As long as they have an iPhone. Just about everyone I know has an Android-based phone, when they have a smartphone at all. Oops.
I would argue that last.fm wasa first massively social music service, and it also shown that social side is not all bright. I made a few good friends there but the amount of hate and loathing in shoutboxes astonishes.