I'd like to take a somewhat contradictory position on the subject. I agree they shouldn't be allowed in places such as Disney for obvious crowding concerns they can actually be very usefull in other situations so I'm quite against the calls to outright ban them. As an adult I own and wear a pair myself, often! They're an excellent way to get to work, for example, and not have to then find somewhere to store them the way you would roller blades for example. It also eliminates the need to bring along shoes to change into upon arrival.
Where I'm from there is a lot of people who want to see even the sale of the "monster shoes" banned. We actually even had a city wide "ban heelies day" where you were supposed to wear shirts given out by city council to support the potential ban. In protest I wore my heelies at work, with the wheels out, in the courtroom (I'm a defense attourney) and the judge actually thought it was a pretty fitting idea for a defense lawyer to "defend" heelies... then he reminded me suits usually go best with dressier shoes and told me I'd be in contempt if I tried it again, lol, but it worked for that day.
Anyway, in conclusion, heelies have some actual uses and if used safely theres little reason for all the hate they're being given. In the two cases of children being smacked into by older kids on heelies brought up in this very thread what was the common factor? Neither time was the parent of the older kid around or at the very least concerned. Are heelies the problem then? No, I'd like to pose the possibility that it's the epidemic of bad parenting thats sweeping the world these days. Think about it, you all jumped on the original poster for trying to find out the RULES so she could make her kid FOLLOW them. Let a good parent like her have a break, try going after the parents of the kids with heelies running down little kids without any regard for their safety.