There's also the power issue. People who hold no power offline find their power on-line and that also explains why people behave differently., usually negatively towards others.
Damn, how much time do you have to spend online to develop an "internet-self?"
People seeking (positive or negative) attention online are obviously compensating for something lacking in their real day-to-day life. That said, I think it's mostly harmless, I certainly have no reason to worry/care about it.
There are different degrees to how different you can be online. Some people at GAF have said that there are slight differences between themselves and their "internet self", but there are just as many people who make up a whole new person.
As for myself, Im pretty sure that if you could ask one of my closest friends if Im the same on and off the internet, they would probably say yes, except that I sound more nerdy by talking about videogames.
That's pretty much how I am...in real life I'm not much of a talker and "goddamn" is about as strong as I get language wise, while online I make Richard Pyror look like Mr Rogers. Other then that, it's more or less the same.
It's pretty obvious that a good number of people have created net personalities for themselves, as it's the only way to make a mark that others could see in an otherwise boring, mudane life. The very concept of giving yourself a "handle" and using an "avatar" to define a personality (and not neccessarily yours) lends itself to such a creation. How much that personality reflects their true inner selves is anyone's guess, though it's safe to say a good number wouldn't have the guts to say some of the shit they do to the average person's face.