I just keep mine on linoleum. The game does not last longer than about 2 minutes, but I get your drift. It could be gross on carpet and painful when the fire ants are moving.

@snytiger6: It would probably be a problem on multi-designed carpet, or if they played and did not eat what came out. So far mine eat mostly all of the food and I always have it on a light solid colored carpet so any leftover food is easy to see. I bought it after reading on ways to keep indoor cats more active and avoid them overeating.

I can understand how you feel, but one of our cats has an eating disorder and he'll compulsively eat and then throw up repeatedly unless he's controlled (he was a rescue from an ugly hoarding environment and still carries those scars two years later).

Our toy is larger than a ball and not as mobile, and while he will drop pieces on the ground, he's obsessive about eating them all, so there's not much mess when he's done.