Saturday I bought the wife a new laptop from Best Buy for Mother's Day. A rather large, yellow-shirted "security guy" bellowed, "Sir, I need to see your receipt." Looking him in the eye, smiling as I walked past him I said, "No, you don't."
On a somewhat sadder side note, I've come to realize how dim the screen on my laptop has become! Lowers. LPKs, laptops, so many Ls, so few Benjamins!
I worked at a "store" a couple years ago as contract armed security and we were told to "check" receipts for a couple weeks - new store. I just simply asked if I could see their receipt. They dropped that after they got the LP guys all settled in though.