In the olden days a sociologist had to find people and recruit them to fill out long arduous forms. Today there is Facebook, and these sociologists are finding out that people generally love to talk about themselves. It is fun to talk about my interests, social networks and life!
Check out the New York Times article ‘On Facebook, Scholars Link Up With Data’. I would imagine this is being used in many other ways and will be being used more frequently in the future.

Yes. Narcissism (i thing, more egomania) take some place in social networks. But it is also a friends network too.It is like proportion:some doze egosim/some piece of great friendship.
With the colossal amount of data and the loyal followers that Facebook has, It's not surprising why scholars use it to make their research. Facebook is one of the most popular social networking platforms where like minds flock together. It is one of the most-trafficked Web sites in the US, and so, it has become an irresistible focal point for several types of academic research in social science, psychology, etc.