It's gross when someone collects old fast food wrappers and toys by the truckload in their house. It probably smells, and it looks horrible. What's even more disgusting is when someone collect cats (or birds or dogs or whatever animal) and their poop up to the rafters. Not only does that definitely smell, but it's potentially lethal. After all, breathing in petrified poop fumes has to be bad for you. And let's not forget the hoarders who don't realize (or don't care) that there are dead pet carcasses stuck somewhere in the refuse. Actually, let's forget that part if we can.