That's fake though. I hate people who "try to be something they're not". Besides, hasn't Holliwood and such taught you to be yourself?
It isn't necessarily "fake." I don't talk about myself, my personal life, or my beliefs online. BUT, I don't talk about that stuff in real life either. It isn't being evasive or mysterious. I just don't think "me" is an interesting topic of conversation. (If someone asks me something personal, I'll be happy to answer, but I don't assume beforehand that they want to know.) Not everyone feels the need to be a walking autobiographical rant machine. As Inkmonkey said, it isn't "professional," but it is also a rather shallow approach to any kind of discussion to be always spouting off all the little boring mundane things about your job, girlfriend, haircut... If you really have to say those things, keep a blog somewhere, so the only people who have to read it are the other self-absorbed people blogging about the same boring garbage.
If you are a self-absorbed asshole, by all means, keep acting that way on forums or whatever, but don't assume everyone who doesn't act the way you do are "fake." Not every person on the internet is out to tell their "life story" to anyone who'll listen.