Yeah it's getting a bit much now. But you can just tell them, that if there's a problem, call the police, and until then, I'll be taking pictures of my child. Of course though, doing what you did, and getting a point & shoot, makes it a whole lot easier.
Never happened to me though...
Erm, nothing new from me really, only this:
https://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs079.snc4/35301_10150232783870215_519430214_13782518_2721509_n.jpg