What a cool concept, although, as gorgonops pointed out, it is vulnerable to some tragedy-of-the-commons problems. They could fix that with closer monitoring by staff, but that would add to the cost. Still, pay someone $10 - $15/hour to keep an eye on things and make sure folks clean up, shouldn't be a big expense compared to the cost of the equipment. The tougher question would be what kind of enforcement mechanism would they have.