Earlier quoted context omitted.
I'm amazed that no one seems to think it's creepy. Go around taking covert photos of strangers these days and see how people react...
It is in public. And if you sneakily take a photo of someone, how would they know to react? On top of that, there are cameras everywhere in public taking covert photos of everyone, I haven't seen anyone react to it.
Try taking a bunch of covert photos then showing your friends: "Hey look at these photos I took of people with my spy cam!" I guarantee the reaction won't be entirely positive.