A very convenient mechanism by which customers of a fast food restaurant can purchase food without leaving their cars.

On a more personal note, it is my opinion that all people everywhere should, at some point in their lives, spend a few months working a drive thru. When performing that job, people gain a much better understanding of just how deeply disturbed the human race is. If this were a requirement, just like registering for the draft, I think people might just be a little more careful about how they behave.

Or not.