We saw kids wearing them in Disney, but many times CMs told them they have to walk, that heely's were not allowed. Most of the times they kids were walking or just starting to go on their heels. They can get hurt pretty bad if they are not careful, as I see many kids even around our local mall using them and almost falling on their butts
From allearsnet.com:
I just read a tip on the All Ears® newsletter that "Heelys" are no longer allowed in Disney World. Can you verify if this is true? I was just buying my niece and nephews Heelys as well as a pair for myself to cruise around the parks on our family reunion event in May. When I was there last year every kid had them on. Has something happened?
Answer:
This is not a new policy. Wheeled footwear such as "Heely"-type shoes, in-line skates, and roller skates have always been banned from the parks. This is also true of scooters and skateboards. It appears that park management has finally decided to fully enforce this rule, probably due to the fact that so many people are suddenly arriving in the parks wearing "Heelys."
I've recently heard rumors that guests wearing "Heelys" were threatened with fines, so to avoid an unpleasant experience, it would be better to leave the wheels at home.