"Jobs is correct to compare Ping to Facebook and Twitter, because its settings for deciding who can follow you borrow from both of those well-established networks. You can choose to approve followers and post listening habits to a limited “circle of friends,” the way Facebook lets you, or you can permit anyone at all to follow you, as in Twitter. But unlike the wide-open spaces of Facebook and Twitter, Ping’s single-minded purpose is to create conversations (and commerce) around music. It watches what you play within iTunes or on your iPhone/iPod Touch, the better to create a profile of your tastes — precisely as Last.fm has done for years with its audioscrobbler plug-in. And in addition to offering customized social music charts that show each user what their friends are listening to (and buying the most) Ping presents that activity to others in a news stream — exactly as Rdio does for music." - Miguel Caetano from Bookmarklet