Apple has the game center where all your scores form your iPhone are automatically loaded into a public database with your friends scores. It's the same for Zynga and Facebook.
The problem is that your social graph on Facebook is probably everyone you've ever met. Google+, on the other hand, feels much more like using email. Circles are kind of like mailing lists which we use to keep in touch with real friends and colleagues. Incidentally, these are also the people we email photos, documents and presentations to.
Circles is at the heart of Google+ because it makes everything they own better. More and more apps are going to move into the cloud and I'm betting that Google+ is going let developers take advantage of this.
The problem is that your social graph on Facebook is probably everyone you've ever met. Google+, on the other hand, feels much more like using email. Circles are kind of like mailing lists which we use to keep in touch with real friends and colleagues. Incidentally, these are also the people we email photos, documents and presentations to.
Circles is at the heart of Google+ because it makes everything they own better. More and more apps are going to move into the cloud and I'm betting that Google+ is going let developers take advantage of this.