Facebook's open graph protocol, a sort of integration of all of the information on Facebook, mostly sits in the background. You listen to a song on Spotify, it posts to Facebook, your friends like and comment--and all of those actions and reactions is part of the open graph. Stamen Design took some of that public data--not all of it is public, but much of it is--and made the Beatquake, a sort of visualizer of music data on Facebook.
Beatquake shows the popularity of songs in specific geographic locations, so you can see how individual songs blow up in different places. It's beautiful and odd, watching personal taste on a large, rhythmic scale like this.