Ever since I got a fridge in my office, I haven't had much use for the office vending machine. Basically only when I don't have what I want pre-stocked in my fridge.
Although, it's interesting to note that the last three times I've been "slumming it" at the vending machine, it has been trying to buy back my loyalty by having there be anywhere from $0.65 to $1.25 in change sitting in the return slot.
It's not like I can go around to an office full of people and say "can you please identify your coins that I found?" and get a straight answer, so basically my last couple vending machine purchases have been free of charge.
My loyalty is not so easily purchased, though, since the machine doesn't have Caffeine-Free Coke.