I have a VERY common name, so I'm hard to pick out from the masses. (There are approximately 6 people at NASA with my first/last name, and for one of those I even share middle initials) Then, I never got into myspace, facebook, etc in college, and after college I got a job that requires me take a yearly training in cybersecurity that says "stay away from social networking" so it's easy to just tell people that I don't have a facebook account because my employer has a preference against it.
That said, Google knows how many peanuts are in my crap, I'm sure. I wonder how much Facebook knows about me, sometimes.