I used to buy a morning coffee from the coffeshop in my office building.  One morning, I grabbed a bottle of water to go with my coffee.  After chatting with the barista, paying, and getting to my desk, I realized I only paid for the coffee because I never set the water bottle on the counter.  On my break, I headed down to the shop, waited in line, and then told them I owed them for a bottle of water.  They were thankful for my honesty but I was amazed that the 5 or 6 people in line behind me all rudely informed me that THEY wouldn't have bothered to come back to pay for a bottle of water.  Even more egregious is the fact that all of those people have to sign an annual ethics agreement at my company to act honestly both in and out of the workplace yet they were all bragging that they would have stolen the water.