It asks too many questions. I don't like having to address a larger issue, like how much information do I want to expose to the world, while I am trying to sign up for something. For instance, it asks for your birthdate. I thought it was just for Facebook records, but I go to my friend's page and lo' there's her age, right at the top of the page.
I skipped most of the rest of the personal information questions, but I can see immediately that the less info you put in, the less likely you'll be able to join networks or recognize others.
Sure, I probably shoud just forget about privacy and put everything up. I notice a lot of people doing that, and my life is quite pedestrian. I guess it's a psychological thing. If I see a camera, I tend to head away from it. Obscurity has its advantages.