I was working today - I work part time in retail, just for a little extra spending money for us all - and there is an escalator in my store. The side facing my counter is the "up" escalator. I saw two boys running DOWN it, and jumping down a few steps from the top. I went over and told them that the escalator is not a toy - not realizing that their father was standing there watching them do this. He didn't seem too impressed with me telling his kids what to do (he made it seem like I was spoiling their fun).
But I just am not sorry! All it takes is one video like to make you never, ever want let a child play silly beggars on an escalator ever again!
(WARNING for video in link: It's a clip from Rescue 911, an old show that did reenactments of emergency situations. This one is called Boy vs. Elevator, so... just be aware that it's a pretty harrowing watch, if you do click through. The harrowing-ness is what made me go after those boys today.)