Is the person you present to others on social networking sites, like this one, myspace, etc. the same person your friends and family know?

I've been involved in a lot of forums, online groups, and social networking sites, and I have to say that I have a sneaking suspiscion that many people present themselves differently online then they do in real life. Some of the things they say, I can't imagine anyone saying in real life, and I've known a lot of not so very nice individuals.

It's lead me to believe that many people, perhaps even most, may use the internet to act out what they really want to say, but feel they would be looked down upon for stating to people in the real world. I think that they might be using an online venue, where they can effectively hide behind their computers, making up entirely different identities half the time, so that they can show their true colors, without ever having to take responsibility for being (insert colorful four letter word here).

To that end, perhaps there is an up side. Perhaps the internet prevents those who would use it for this purpose from actually running out and harming society. Perhaps then it is a useful therapeutic tool. Still, I'd much rather people just be honest and own up to who they are, and what they are, taking the consequences with it.

Have you, in your experience online, done this or known someone who did? Have you ever thought along the same lines that I am now, about why someone would, or that they do in the first place? Any theories?