Over on my reputation research blog, I wrote a post that applies to our Yahoo! work too.
It’s on the concept of “negative identity”: perhaps social identity formation consists of an element of defining yourself by what you are not. That is, you don’t always actively define your identity in terms of all the things you like to do, but instead, by who you are not and by what you don’t like.
Most social networking sites tend to allow users to define themselves only by what they are: that is, what are your favorite hobbies, music, movies, etc.? Who are your friends? But you don’t really use social groups on social networking sites to keep other groups out, do you?
Anyway, check my post out.