Are photographers a threat?

From Bruce Schneier:

What is it with photographers these days? Are they really all terrorists, or does everyone just think they are?

Since 9/11, there has been an increasing war on photography. Photographers have been harrassed, questioned, detained, arrested or worse, and declared to be unwelcome. We’ve been repeatedly told to watch out for photographers, especially suspicious ones. Clearly any terrorist is going to first photograph his target, so vigilance is required.

Except that it’s nonsense. The 9/11 terrorists didn’t photograph anything. Nor did the London transport bombers, the Madrid 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?