The picking on kids who're just drawing for fun thing really gets my goat. My husband has an amazing eye for art, he gives me some of the best advice I've gotten anywhere, but he can't draw hardly at all himself, and it's largely because he got too much harsh crit as a kid, and decided that meant he didn't have talent, and left off. He's mentioned a few times that he wishes he'd been able to ignore it and keep on.

Being harsh to kids who are just having fun is not helping anybody. Heck, being harsh to adults who are just having fun doesn't help either.

Honestly I really think that crit should be given when asked for, or people should go "do you want crit?" before offering it up. Otherwise you may just be spoiling somebody's "just for fun" good time, and ruining their desire to do any art at all.