Stan Schroder, on Mashable, looks at aggregation of Social Networks. He quotes Kottke discussing different social networks:
since all of them require different credentials to log in, theyre just adding to the noise
20 different tools are listed, most, though not all, are websites. Not that many seem to include Facebook in their set of supported Networks (though I am only basing this on the information Schroder supplies). I’ve used Ex.plode.us (an Elgg based tool) – which is one of those that doesn’t work with Facebook. Profilefly is a Facebook application (I think you can use the Website as well)- so that will bring in information – but I’m not sure how well it works getting information from Facebook.
I’m also not sure with any of these (other than Ex.plode.us) if you have to have an account at all of the sites that they integrate, or if, in the same way that Meebo allows your AIM account to communicate with your friends MSN account, you only need to have one account, and just know your friends identities in other systems.
Ex.plode.us does seem to do that, albeit only over a limited number of networks.