told the person in front of me paid for my meal (the person in front of him paid for his, etc.). She asks if I want to do the same.

Person in front of me looks in mirror and sees one person in car/hears my total and says "sure, why not?" He got a deal as there were three in his car/order.

Behind me is a van full of people and my "pay-it-forward" bill is going to be about 6-7 time greater than I would have paid for my own. I opted out.

Got the look of death from drive-through girl like I was a bad person for not continuing the streak. I enjoyed my free meal.