Imagine you are given a pile of tokens, representing real money, and invited to donate to a common pot. There are other players but you can’t interact with them. The sum of collective contributions will be trebled, then shared equally among all players. What do you do?
If everyone submits all their money, all get richer. But if everyone except you pays in, you can enjoy the collective payout while retaining your original stash. The flaw in the selfish strategy is that other people might have the same idea. If no one pays in, there is no bounty to share.
