If you're using multiple social web services, you will also have multiple online identities. For creating a comprehensive online persona, consolidation between the various profiles would be useful.
Having a portable online identity and contact network would be very useful, as it would make signing up and using new web services much easier. Instead of having to invite all your friends multiple times, you would just point to some of your existing profiles and the service would gather your contacts and profile information from there.
To experiment with the concept I added my various online profiles into my home page, and gave the URL to Plaxo's Online Identity Consolidator. It was able to find quite a good set of profiles and connect them to me:
Updated 14:52Z: Very good write-up on Bokardo