I was in a local discount department store, having a big box retail orgy. As I pushed my cart through the security scanners on the way out the door, I beeped.
The security guard grabbed my receipt to look. "Oh! Must be the batteries." So he starts rummaging through my bags trying to find the pack of batteries that's in there. "Oh, wait, you have a DVD-- I'll bet that's it."
He grabs the DVD, waves it through the scanner, and when there's no beep he puts it back in the bag. Next we dig out the batteries, and he repeats the process, but they don't beep either.
So now, having convinced himself that the things I've actually purchased aren't setting off the alarm, he ignores the possibility of my having stolen goods, and waves me through. (beep beep beep)