I have a young child - he's two and a half. Most people are considerate and ask if it's OK to take a photo - and I generally say yes if it's friends - but we were at a wedding recently and a staff member, total stranger, at the venue was laughing at him running around and asked if they could take a picture, and then got stroppy when I said no. I just think it's quite strange behaviour to want to take photos of a child you don't know. It's quite different to the professional photographer taking photos for the hosts in my mind, which you basically accept by bringing your kids to an event like that.

A mum at a playgroup just took out phone and started filming my son playing with her child. My wife asked her to stop and she again got quite stroppy, even though the group explicitly said that photos should only be taken with consent in that space!