Everyone can be a member however it depends to you and the the people who develop the site.
Facebook, with over 10 million members.
Eish
I don't now exactly the figure but I am sure it reached millions already.
Fitlads is a social network for homosexual males that want to meet new friends, find a romantic partner, or just find someone to talk. It currently has over 3,400 members and is centered in the United Kingdom.
International Network for Social Network Analysis was created in 1977.
The main objective of a social networking site is to bring people together and get them to stay connected to each other. This happens through members posting status updates, sharing photos, and generally conversing with their network.
The social Network
The duration of The Social Network is 2.02 hours.
Path - social network - was created in 2010.
Facebook is an example of a social network platform.
The Sphere - social network - was created in 2008.
Social Development Network was created in 1984.