I have to laugh at this one. I was in a Costco a few days ago on my Hawaii vacation. A family with about 6 boys ages 8 - 20 were in the food court line ahead of me. They were basically playing tag with a gecko, putting it on each other's shirts etc. They kept jumping around almost hitting me or jumping on my feet. Their parents stood right there and said nothing - even though they were clearly bothering the people in front of them and behind them (me). When it came time to order they hadn't made any decisions and stood there in a large group arguing while everyone else tried to scoot around them. I have to admit, I made a few pointed remarks to them about their behavior - which were ignored.
So I have to add - no boisterous games of tag (especially involving lizards, insects, etc.) while in line!