Many many years ago, some of my relatives were at the beach in CT and took some Super 8 home movie footage. When they got it back from the developer, they were surprised to find a card stating that some footage had been removed because apparently it showed a US submarine from Groton. Naturally I heard this story later when my grandmother had her home movies transferred to VHS -- there's still a blank spot maybe thirty seconds long.
How the government stayed on top of that, I don't know. Must've been a lot of trouble. And probably a submarine of secret design wasn't supposed to be from Rocky Neck -- that one day alone, hundreds of people could've accidentally photographed it. But that's not alarming censorship. The feds didn't show up at my grandparents' house to hassle them. There was just a brief apologetic card and some blank film. And it was a freaking submarine.
Getting paranoid about people taking photographs of generic public structures is deeply, deeply stupid. Especially since much better photographs of them are commonly available. And the people poisoning the water supply in Kalamazoo aren't terrorists -- someone may have cut the fence, but the oil company just dumped a ton of oil into the river there . . . and waited way too long to tell anyone.