In Facebook's terms, the social graph is the name given to the collective pool of information shared between friends that are connected via the site.

BBC: Facebook unveils social search tools for users

Will Graph search (the name is terrible for the average user) be another flop, or it will it really change how we search for relevant things in the future.

FORBES: Connect

It hasn't been given a name yet so lets reference it as "The Big Graph" where all lines intersect at 2020.

CNN: Just Imagine - Living Space: Your views