Not to belittle any of your opinions, but I've been amazed at how YOUNG the kids are that I see on these things. I see kids that I swear look 5 that can Heely pretty good, and I've never seen anyone nearly run into anyone. I have seen kids in restaraunts, Wal-Mart, malls, etc on them but I've never seen them rampant like skateboards used to be. I usually only see them in short little bursts of 5-10' at the most and then they stop and continue walking. I was also in Disney 5 weeks ago and I don't know that I could even recall seeing one kid on them, I'm sure there were some, it just doesn't stand out to me.
As for parents allowing them, you just have to remember that there are a lot of dumb/rude/ignorant people nowadays that have NO MANNERS. It irritates me just as bad as you guys seem to see an adult standing right outside the door to a restaraunt blowing smoke so you have to walk through it to get into a non smoking establishment. These are the kind of parents (not just rude smokers but the mentality of these people) that don't care that their kids are Heelying all over the place or telling them to put them back in once they get trhough the gate. They have no respect for anyone else and are passing it on to their kids.