Marty Cox walked into the same coffeehouse he’d been going to for years, ordered his usual coffee, and reached into his pocket for his wallet. Oops, no wallet. No problem, said the owner, who recognized Cox as a regular customer. Pay for it tomorrow. The next morning Cox walked into the coffeehouse, money in hand to pay for yesterday’s coffee. The place was packed with customers. Suddenly the owner hollered out to Cox, wanting to know whether he ever paid for that coffee.