I'm afraid one of my kids is a little scammer in the making. I hope I was able to show her it never really works!
BG: We were at Target one day and I got the kids their school backpacks. As we were leaving, the security gates went off. No one ever came over to investigate but I made sure the kids didn't accidentally have anything in their hands or pockets (they didn't.) Of course, I had the receipt for everything in our bag, so we went on our merry way. At home, I discovered one of those square security label things and I figure it was either supposed to be removed or disabled in some way and wasn't. The kids were very concerned about the whole "gates going off" thing but I told that sometimes they do and as long as you aren't actually stealing anything, it's not a big deal because you'll have a receipt showing proof of payment.
So in the car the other day, DD8 (who has obviously been mulling this over) said, "Mom, I know how you can get past the gates!"
Me:

Oh? How?
DD8: Well, you just buy something. Then you go back later and steal the same thing but bring your receipt. Then when the gates go off, you just say, "Oh, it's okay, I have a receipt right here!" and then you have two things!
Me:

Well, that sounds like it would work but every receipt has the date and time stamped on it. The security guard would know you're lying.
DD8: Oh. I guess I didn't think of that.
Me:

Well, please remember that stealing is ALWAYS wrong* and you will eventually get caught and it's really not ever worth it. Dad and I will be extremely disappointed if we ever find out you're doing something like that. (then I went into how it seems harmless but it really hurts everyone, yadda yadda yadda...)
She's a really good kid and I doubt she ever would steal anything. She likes a good puzzle and went about solving the problem of security gates. But her logic scared me a little, LOL.
*I know there are circumstances where this could be debated but I didn't need to get into semantics with an 8-year old with a plan to successfully boost merchandise...