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.