This article from Selena Larson on ReadWrite is pretty close to what I was trying to articulate yesterday. There are a few particularly interesting sections.
I agree, on principle, but a lot of this information I think is shared to my advantage. Movies, music, trivial information that I would freely share with anyone if asked. But then there's the more private, and more useful to Facebook, information. It's possible for Facebook, given appropriate permissions, to track where you are and when; this is a significant insight into your life that you wouldn't necessarily choose to freely share. This is the kind of information that I have more concern over.
I can relate to this to a point. In the last few years in particular friends have been experiencing those awfully adult, responsible life changes like marriage and parenthood, advancing careers and the like. These events move people around and change their prioritues. Facebook is an excellent medium for maintaining contact, even if that contact is at times insubstantial. Insubstantial is not the same as ineffective.