So I work at a very large theatre chain in Canada. I was working in concession and a Korean couple comes up and buys popcorn and a drink, nothing special.
As required, I ask the guest if they have our loyalty card.
Me: Do you have a "Loyalty" Card?
Them: No. Does it give you anything?
Me: Yes, a 10% discount.
Them: Oh, a "loyalty" card? I have the number.
Me: Sure, a number or barcode works just fine.
The man takes out his phone and begins reading the number. Our loyalty cards all start with the same 6 digits and his didn't so I knew something was up.
I ask to see the phone and surely enough, something was wrong.
Me: Sir, this isn't a number for a "loyalty" card, this is a Social Insurance Number (our equivalent to a U.S. Social Security Number). You shouldn't give this out to people, it's very dangerous.
The man had a photograph of a piece of paper with a SIN. I don't know whose it was but still, he shouldn't give that out to people.
They had pretty thick accents and I'm pretty sure they confused SIN with our loyalty card, which has a vaguely similar sounding name.