BT's chief security technology officer, Bruce Schneier, has an excellent piece at The Guardian about photographer's rights in this topsy turvy world of the "Global War on Terror":
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 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.
Go read the rest. And after that, go take some photographs of some statues and monuments. And if you live in the US, you might want to keep this document handy.