How is it that we can put a man on the moon, but we can't reliably get a bag of potato chips out of a giant automated box? Is there anything less dependable, yet more tempting, than a vending machine? I always tell myself I don't need the calories or the stress, but when break time rolls around, I'm trying to fish a trapped 50 cent bag of Cheetos from behind the glass.
Seriously, think of how many machines out there that have labels on them of what you should not do when they don't work. Vending machines have to warn people not to shake them because they could potentially be crushed to death. Yet, they seem to know it will inevitably happen because people are so frustrated!