Mine's purely about privacy. I use it wherever I don't need to be my real self online. It first happened when I was filling out some web form and was thinking "Don't you wish" when they asked me for my personal info. That became 'Don Chuwish' and an email address of donchu@writeme.com - "Don't you write me". It stuck.

-Don (well, not really)


(EDIT: Talking about my nickname obviously since I don't even have an avatar. But now, oddly, I'm thinking I need to pick one out!)