I understand your frustration. Recently at the play area in the Ikea restaurant, I had to speak to a little boy who was bossing my children around and put his hands on my son. I couldn't tell who his mother was, so I looked him in the eye and said in a calm but stern voice, "take your hands off my son". After that he backed off and didn't go near either of my children.
Melissa had the opposite experience this summer. Read about it in her blog about "disciplining moms".
