Sjöberg's Law of Public Cliquishness

From the Brunching Shuttlecocks :

Sjöberg's Law of Public Cliquishness

Any unmoderated public discussion space, no matter what the ostensible subject, will eventually attract a clique of contributors who will use the space primarily to discuss their personal lives and trade in-jokes. In addition, it will attract at least one regular contributor who will make it his or her goal to harass and harangue the other regulars.

See #everything, The Everything In-Crowd, Everything Smurfs, and KaZe JoNeS.