This idea has been rattling around my head for a while. Let's say you have five people in a room. Four have either a favorable or shrugging approach to surveillance either in the form of cameras at intersections, GPS tracking in iPhones, or other manifestations. The fifth person is opposed to it. The way that surveillance works in this situation is that people volunteer to report the GPS coordinates of their silhouettes. Let's say this takes place in 2050. We have finer-grained GPS now, and if you favor radical "sharing", you can elect to broadcast a three-dimensional map of your silhouette 24 hours a day. A certain part of the population thinks this is cool. So the point of this picture is that the silhouette of the fifth person may be able to be derived from the silhouettes of the other four and the rectangular box they are sitting in. So we have this 5th person who is a privacy advocate, or worries about false positives, and so has taken advantage of government and/or corporate Opt Out mechanisms.
I think this can be extrapolated to some other kinds of things. I don't have the data but intuitively I feel that process of elimination is something to bear in mind. Suppose that at some point in the near future, we have additional intrusive surveillance systems in U.S. society but our way of trying to be fair about it is to institute "Do-Not-Track" lists. Depending upon other factors, the person who has opted out may still be trackable by something like the "negative space" story.