Think of it: if you want a strong identity, you want one that is backed by financial information. That makes banks great natural identity providers. But financial institutions don’t seem to be interested in this space, and/or regulatory issues are in the way.
There is an interesting post by Om Malik over at GigaOm suggesting how Google can get it mojo back from Facebook.
Taking a slight spin on this, I make the observation that a large part of Facebook's value is your identity and your associations and Facebook's willingness to leverage this information elsewhere on the web (Facebook Connect). Facebook Connect is becoming the most common way to login to other sites. The reputation of your identity is increased by your associations: it requires a consipricy to create a fake Facebook account and have N friends, the presence of which increases your identity's reputation.