This move seems another smart step toward a hybrid strategy: Allow app makers (and Facebook) to extend social-graph functionality to the web, gather more app users, and recruit more members--but retain full control over the social graph itself.
This is precisely the approach we are taking with Notches. A "walled garden" is nice because you retain all control, but these days you need to be open to succeed. If you truly believe in being open, then you're willing to let go of a little control in the short-term because of the long-term value that comes back.
It may not be exactly what Stephen was looking for, but it's certainly a start, right?
(By the way, did you notice they are partnering with Amazon Web Services as well?)