The prevent defense is the battlefield equivalent of a retreat. You retreat all the way back to your end zone where you are forced to make a goal line stand to win the game, and hope for time to run out before they score. If you are going to lose, at least go down fighting.
Great & concise description of the prevent defense. Best I have ever heard. I will use this example when I talk football to folks or on-line, but of course I will take full credit for thinking of it.