Anyone can. That's the problem. The vast majority of them are rented by people who are too obese or lazy to simply walk. They don't use them in the real world, so they have no clue how to operate them. It's become an 'in' thing to rent them to avoid actually physical activity like ... say walking.
They run over people (and children and those who are frail but not lazy and actually walk)... they gouge out and damage walls and wooden doorframes ... WDI now has to design things that take these monstrosities into account because of all the damage they are actually doing.
Funny thing is you don't see them at Disney's parks in Paris and Hong Kong (Tokyo too, but since I haven't been there I'm just going on word of friends) ... of course, they also don't have stroller issues there because they actually make children do something healthy and unheard of here ... namely WALK!