I think people definitely have different personas (personae?), depending on the situation/audience. For example, when I'm at work, talking with clients, I present myself as professional and helpful. In real life, I'm kind of wacky and sarcastic and I have a sick sense of humor. That probably wouldn't go over very well with clients.

I dated a guy once who was very good at making himself be whomever he needed to be to get what he wanted. He could turn his emotions off and on at will. I think that's because he never really felt those emotions, he just knew how they should look based on observing others. It was really kind of fascinating to watch him in action. He never really had any long term relationships and I think that's because he never truly showed anyone who he really was, for real. It makes me sad for him.