In anonymity our true natures are made manifest.
What people do when they think they aren’t being watched can be truly staggering. I think most everyone goes through that period of being insane when they first get the Internet and think that no one can track them. I’m not saying that posting racy fanfic is insane by any means, but you get the idea. A mask, or at least the perception of one, allows the hidden self to run rampant and everyone has one. The person who protests loudest that they don’t is without doubt the one with the most to hide. Like a republican senator crusading against gay rights getting blown by a dude in a public restroom.
Some sites pander to this desire for anonymity, like the various incarnations of fandom secrets or 4chan.
The other side of that is doing insane things BECAUSE we are being watched. Everyone goes through that on the net too. For me it was with Livejournal. It took some time, but eventually I grew out of it, thankfully. Now I try to keep my public displays of insanity to a minimum. I’m only human though, so sometimes it gets out, or I get outed. At those times it’s generally best to own it and move on.
My experiences with both sides of this phenomenon have made me much more tolerant that I once was. Everyone has secrets. When exposed very few of those secrets deserve the scorn people heap on them.