People flush fish, keep them in poor conditions, etc. When I was in College one guy had fish and one of the big attractions was the live feeding of a carnivorous fish. The spectacle would last a few days as the carnivorous fish took a bite out of the feeder whenever he was hungry -- after a few days the feeder would die and the carnivorous fish would lose interest. Eventually the carnivorous fish ate a neon and died. A neon's defense is that it is quite toxic to another fish that eats it.
People that own snakes or other carnivorous animals will often times use rats or mice as 'feeders'. Depending on the size of the snake, larger 'feeder' animals are used, from rabbits up to small dogs. I don't know how often guinea pigs are used, but it is not a good practice.
It is an unnatural setup, it does not mirror nature since there is no way for the prey animal to escape as in the wild. If attacked in the wild, most prey animals have defenses -- guinea pigs for instance will know the surrounding terrain and have good pathing ability -- so they at least have a chance of survival. If you toss a prey animal in a cage with a snake, unless the snake becomes uninterested there is no way the prey animal is going to survive the ordeal.
Personally I have never been that interested in wall-mart. They seem to have a lot of things, but they never have much that I want. Even if they do have what I want, I have trouble finding anything specific in the store. I shop at Costco and some of the other warehouse type stores (Fry's, Factory Direct Furniture, etc.) I believe wall-mart uses a computer program to layout the store in a 'strategic' fashion (make items harder to find, place certain items close together, etc.) I don't have time for that.
Union workers at the local supermarkets can make 20-30USD/hr depending on what they do (ie. grocery baggers make less than meat packers). What people don't realise is that not anybody can just walk into a supermarket like this and get hired. Obviously a job that requires no skills and pays 20-30USD is quite sought after. A common person can't get this type of job, short of knowing someone in the union or having a parent/friend in some important government position.