Nice question, lol.
But then who's really gonna come and confess their true nature if their online fronts offer them "respect", "power" and "leetness".
(Or if it's their hobby to troll and annoy other people)
-This is a question that should be asked on like a WoW forum where the difference may truly be frightening, lol
So i guess you mean 'for forums' then like this.
My online personna offers the surface of me. What I present isn't false, it's just not everything.
If I meet up with someone offline, they'll see more depth to add to how I've presented myself online.
Then again (from experience) it's a matter of perception from the other person. No matter how you present yourself, with some people you'll mesh, with others you'll not.
People have a habit to see only what they wanna see...