Owing to the "dominant strategy" (or the strategy that is best for one player when they do not know how the other player will act), the Prisoners' Dilemma illustrates why cooperation is difficult to maintain, even when it is mutually beneficial for the captured prisoners to cooperate.

Still, people sometimes DO cooperate:

• When the Prisoners’ Dilemma game is repeated a number of times (to illustrate the preferred outcome); and

• As a result of the [purposeful or accidental] use of a “tit-for-tat” strategy.

The “tit-for-tat” strategy includes mimicking your rival’s action – renege or cooperate – in subsequent rounds of play.

The non cooperative oligopoly equilibrium is bad for oligopoly firms (prevents them from achieving monopoly profits) and is good for society (with Q closer to the socially efficient output and P closer to MC). Still, in other types of prisoner's dilemmas, the inability to cooperate may reduce social welfare (e.g., arms race, overuse of common resources, etc.).