First time I was told not to take pictures. A manager approached me and said that the owner doesn't like people taking pictures here. (he was polite about it)
So I went and knocked their toilet paper aisle over. (just kidding)
I understand that to them, I could be "casing" the store for a burglary or something, or "spying" for a competing store, or some other heinous act. (maybe I was just in the way in an abandoned aisle, or scaring other customers) It's obvious that I'm up to no good, and perhaps I overreact by moving 2 states away...at least I got a cool HDR out of it.