Tim Bray is on to something…
You should check out http://www.tbray.org/ongoing/When/200x/2008/05/05/Changing-Your-Address.
Tim is explaining in a real-world scenario the exact idea around the “Infobus“.
This is all about liberating your data.
Imagine if Amazon could access a feed (that you provided and gave them access to) containing the names of all your purchased books rather than storing all this information “for you”.
It is your data after all — why not liberate it — think OpenID writ large.