Every single person here should be incredibly concerned about the growth of Facebook, it's integration into virtually all aspects of life, and how it provides a means for corporate interests -- or really, anyone with money to spend -- to track every public movement and thought of yours at all times.
But that possibility only exists if you let it. If you're concerned about people being able to track every aspect of your life on Facebook maybe you should, you know, not post every aspect of your life on Facebook.