I don't think people who label themselves as not being very social are saying that they aren't social whatsoever--just that they aren't as outgoing as most other people. And that can come from a variety of things. For me, for example, I was teased a lot as a kid growing up for my social awkwardness, my weight, my appearance--anything and everything, really--and I took it to heart and believed that no one really enjoyed my presence, so I became withdrawn and wasn't very outgoing in the real world until I got to college. I found that communicating online was a lot easier for me because I feel that I'm generally more eloquent in writing than in speech, and because I don't have to physically look at someone. When people look at me, part of me still fears that they're judging me negatively...and looking someone directly in the eyes is hardest, because I feel that if they're looking back at me in my eyes, they're able to search inside me to find something they can use to destroy me. Very paranoid, I know, and I've gotten better about it, but this is what bullying can do to people growing up.