Can anybody tell me how the data in social networking sites is organised??
And why are you expecting quick replies from a forum of volunteers?
Especially since the only people who would know the answer to how data in any application is organized would be the people that work with it and would be ethically - if not legally - constrained by trade secrets, non-disclosure, etc. it would be shocking if anyone provided an answer in any detail at all.
What is your purpose in asking?