For me, that's a simple question to answer. I don't like the (Internet) places that ask you to "tell all" before you even know what the place is like. I want to hang out, and find out if it's a "Safe place" for me to share that information. Now that I've been here a while and like this place, then I went back and shared info on myself. I guess it's for my own safety, and if I leave a place and haven't given my personal information, then I never have to worry about it getting out without my permission.
It's the internet, you can never be too careful!