It's becoming increasingly common to "meet" someone online before you encounter them in real life. In my experience, people I meet online are generally quite recognizable when I finally get together with them at a conference or physical meeting. But maybe I'm just lucky.
A fascinating study by Max Weisbuch, Zorana Ivcevic, and Nalini Ambady shows that - in large part - we really are who we pose as on Facebook. The article's from Cognitive Daily. I do think we tend to present a idealized version of ourselves - the cool side of our lives we want everyone to perceive as us. But then again, we also do that in face-to-face relationships, don't we?