An interactive “Provider Guide” provided by JanRain shows what personal profile data maintained by popular social networks is available to applications that connect to these networks.  It is not surprising that Facebook offers the most information; LinkedIn is second in terms of available profile attributes.

With these many attributes about subscriber identities available through published API’s, it isn’t surprising how the stock market placed a huge premium on LinkedIn, and will presumable do the same with Facebook.  Perhaps the most valuable attributes are the connections to other people – friends on Facebook, contacts on LinkedIn.  The Network Effect arising from the interconnectivity of all those online members triggers extreme value momentum, particularly when all those relationships can be exposed to third parties.