Thanks bruce. Yes, Linkedin is for sure the professional destination. Users are slightly hesitant to give out linkedin data, Facebook has a 5x larger userbase and people tend to fill minimal data such as job title and education, so the idea is to build and use a professional graph so as to interpret relevant information to the data and quantify it. There is some useful info such as interests, likes, groups etc which give vital information too.
The plan is to integrate all possible social sites and aggregate the professional data out of it.