Prepay groceries seems like it could be an ideal solution for grocery stores. They then have predictable fixed income, they eliminate credit card fees which eat away their profits, they increase customer loyalty, and they have the ability to potentially offer more customized and personalized service to consumers. I'd imagine it working one of a couple of ways:
1. I sign up and I setup an automatic withdrawal for 75% of my grocery budget each month ($300). If I don't spend all of the $300 it rolls over to the next month, but I can't get a refund. Funds that roll over could either reduce the current month's withdrawal or perhaps a 5% bonus could be added to the amount as incentive.
2. I sign up for set my $300 withdrawal and the store gives me a bulk buyer discount (say 10% off any prepay purchase).
As additional incentive the company could provide highly customized newsletters (exotic fruit month, come in for free samples and discounts), interactive website, in store and online classes, ask a grocer Saturdays, etc etc. Basically specialize in quality, variety, and geek services rather than marketing and loss leaders.