The two previous posts by Tony and Tom were interesting. I think the harassing of newbies in chat environments indeed is a common phenomenon. I've only spent a small amount of time in IRC, AOL chat rooms... have done quite a bit of browsing of newsgroups... and have spent considerable amount of time in the multimedia community called "Palace." Harassing newbies is NOT tolerated by the people who run the TPI (The Palace Incorporated) sites, so I'm surprised at AOLs reaction to what happened to Tony (AOL probably wasn't happy about your exposing their difficulty in controlling unpleasant behavior, which is an ongoing problem for AOL).
IMHO, harassing newbies in the name of an "initiation rite" is an immature adolescent attitude based on underlying feelings of insecurity. Online communities often can be very tenuous, people come and go, and making your "mark" is not easy. So if people do succeed in becoming a "regular," but still feel a bit of unconscious worry about whether they are REALLY important, they'll act out that insecurity by picking on newbies.
"Doing unto others the bad stuff that was done to you" is regressive behavior. It's what psychologists call "turning the passive into the active." People who once were helpless victims of abuse later try to master that feeling by actively inflicting abuse onto other helpless people. It makes them feel powerful, important, and in control.