[X-Cubed]

The machine could add each code to an internal blacklist after each use. It doesn't prevent the same code being used with another machine, but it would prevent coffee vendors from providing boxes of K-cups that are all printed with a single code.

[Zikes]

Those vendors could acquire new codes as easily as making a trip to the store. Heck, they could even incentivize customers to snap a photo of an authentic K-cup's code and tweet it to them, maybe for a coupon or imaginary internet points. As long as they had enough codes to make sure any given pallet didn't have any duplicates, they could be 99% certain a customer wouldn't get repeats, especially if they retired codes after a certain number of printings.