Really quick, I just wanted to jump in and say, with regards to Facebook privacy, there is another situation that I have yet to see adequately described. The situation I am seeing described is when you publish a piece of yourself, and it goes further afield than you anticipated, ie you share photos with someone with whom you had no intention of sharing.
But consider the obverse situation, when you publish a piece of yourself to your social circle, and it is withheld for some reason from a portion of this circle because of a change in privacy setting, or confusion about the impact of the privacy settings you have selected.
In many ways, this may create more distrust in the platform, when someone in your social circle feels slighted because they did not receive the expected update. Of course, this happens with email spam filters as well as social network privacy settings. In either case, it creates an atmosphere of distrust in the platform.