Have you ever wondered why debates about politics, constitutional law, and philosophy can go on and on without end? More generally, why do people like to argue over such pointless matters? Even yours truly recently fell into this trap on Twitter, where Jonathan G. Harris (@jgharris7) and I debated the question, what is the optimal level of regulation? (The entire thread is available here.)
As it happens, our friend and colleague Bryan Caplan explains here why certain types of arguments resemble a Prisoner’s Dilemma:
If your opponent keeps arguing, you want to keep arguing so it doesn’t look like you’ve run out of arguments.
If your opponent stops arguing, you want to keep arguing to emphasize that your opponent has run out of arguments.
As a result, both sides have an incentive to argue interminably. Which, as you may have noticed, they usually do.
In other words, there are times when making an argument is like the “defection” strategy in the Prisoner’s Dilemma, while maintaining silence is tantamount to cooperation! Do you agree with Professor Caplan’s analysis?
prior probability 
Some people just like to argue for the intellectual stimulation of it, and perhaps the excitement of it, like fencing. I tend to make my points and fold quickly. Therefore, many (most?) arguments are not like Prisoner’s Dilemma, in that they are not zero-sum. Both can walk away feeling they have won, in fact it is probably rare for both participants to have the same payoff matrix.
I mangled my point by implying that Prisoner’s Dilemma is a zero-sum game, which it is not… what I MEANT to say was both “players” can walk away with a positive payoff in their own minds, without much regard to what their opponent does — which is unlike P.D.
Hear, hear!