[pandaman]

They could have used thermo-sensitive ink (using same technology that fax paper used some time ago), on a hot cup it would have automatically destroyed itself. However, they very likely don't care about the replay hack.

The authentication scheme is there to prevent mass-manufacturing counterfeit cups. Hipsters who modify devices are below noise level on their bottom line (them bragging about sticking it to the Man is free advertisement for the brand so even if there were a loss on a machine it's hard to tell if there is a net loss or profit).