This is a great idea. One possible thought would be to write an integration into Facebook or LinkedIn and leverage those applications to do the social demographic context mapping.

You could request that all your contacts have at least one account in either platform. To simplify I would recommend you pick one to make the social demographics mapping simpler as one integration.

The way I see this working is that the integration would do a query on your contacts to the LinkedIn or FaceBook database, did a match, which is then mapped and validated. Once mapped a reverse query could be run from their Facebook or LinkedIn network to your SFDC contacts.

When a match is found they could validate it to avoid duplicates and confirm that they know the person. in Contacts you could have force.Com page which pulls in the matches as an small table that shows people they know or lunch a pop-up that shows a force.com page with the scrollable list.

Once that is enabled you could write report which shows the relationships to allow your account mangers to do account planning session based on your collective social network demographics. I could see this leveraged for setting up meetings as well on common topics or small group networking to build collaboration communities of practices.

Anyway that is my two cents. I think this has lots of posisblities.