Whilst not scientific at all, a webcomic I read did come up with this:
Human + Anonymity + Audience = Idiot.
Of course they were referring to the people you have to endure when playing games online but I think the theory is sound(ish)
I'm quieter in real life.
I find it hard to articulate my thoughts when speaking so end up babbling and losing the interest of whomever I'm talking to. Much prefer to communicate through text. Gives me time to organise my thoughts and get across what I intend to say.