Terrorists don't take pictures as much as photographers

You may have been following news stories that show security guards harassing citizens in malls, libraries, and train stations across the country. Here's a good one where, while the railway authority insists on-camera that they don't ban photography, they are interrupted by a security guard demanding that the camera be turned off.

Bruce Schneier is brilliant (as always) in his discussion of the ban on photography in the effort to stop terrorists:

Except that it's nonsense. The 9/11 terrorists didn't photograph anything. Nor did the London transport bombers, the Madrid subway bombers, or the liquid bombers arrested in 2006. Timothy McVeigh didn't photograph the Oklahoma City Federal Building. The Unabomber didn't photograph anything; neither did shoe-bomber Richard Reid. Photographs aren't being found amongst the papers of Palestinian suicide bombers. The IRA wasn't known for its photography. Even those manufactured terrorist plots that the US government likes to talk about -- the Ft. Dix terrorists, the JFK airport bombers, the Miami 7, the Lackawanna 6 -- no photography.

Given that real terrorists, and even wannabe terrorists, don't seem to photograph anything, why is it such pervasive conventional wisdom that terrorists photograph their targets? Why are our fears so great that we have no choice but to be suspicious of any photographer?