About 8 or so years ago my friends and I had a pretty ingenious scam related to an unnamed electronic store. What we would do is go into the store and buy a cheap CD. We would walk out wait a few hours and bring the purchased CD back in to "return it." At this store when someone wants to return an item they merely place a little pink sticker on the item and send you to the returns desk.

Well....we would carefully take off the pink return sticker and plop it on an expensive software box such as windows XP. We would then take that to the desk, say we lost the receipt and they would give you store credit....an easy $300 or so with a $10 investment. We did this all summer and finally they caught on and started asking any customer returning any item w/o a receipt to provide a drivers lisence and would limit customers to doing this only 5 times per year.

So ya.... :-D