What's interesting is how the macro-cooperation game gets completely ignored by so many people when they play a game like this. If you're never going to interact with someone again, then betrayal has no long term consequences, but if it's someone you plan to continue a relationship with in real life, then betrayal, even if it's "just a game", will damage that relationship, possibly terminally so.
It's almost like our instinctive zero-sum behaviors short-circuit our higher reasoning just enough in this simulated environment to suppress thought of the long term real-world relational consequences of our actions.