Calling it a zero-sum game makes it sound like some people are exploiting others. You can make the same argument with gold by saying that, if everybody stopped

Calling it a zero-sum game makes it sound like some people are exploiting others. You can make the same argument with gold by saying that, if everybody stopped caring about gold on the same day, then everybody owning gold would be big losers in the zero-sum game of gold. Moreover, the argument that the cited video makes about criminals using the currency (i.e. "honor among thieves" doesn't exist) is fundamentally at odds with the concept of the infinitely iterated prisoner's dilemma. That's why the whole concept of "reputation" envolved (in Nature and online). Someone with 98.7% positive feedback might screw you to save $50, but doing so would not be beneficial in the long run.