I'm going to disagree with the thoughts that tons of other people are collecting receipts. I really don't think that a large number of other people are on to this too. Sure, some people have found a receipt or two and thought to scan it but realistically how many people is this and how many are doing it for sport? Right now we are in prime summer holiday time, across the board stores are quiet. Second to that, most of us have been conditioned not to litter so people just don't leave things in the cart when there is a garbage bin right there.
BTW, found a receipt yesterday that was a SCORE...had 3 strawberries, 2 wraps, cherries, zucchini, eggs and burgers. I left work at noon and decided to grab something nice for lunch so I drove over to Fortinos. It was well worth the little drive.