Challenges with point-of-sale devices
The point-of-sale devices that retail operations use need to be very easy to use because they're often used by relatively untrained people. I saw an example of this a few years ago when I went to the local sporting goods store to pick up a package of white athletic socks.
I handed my credit card to the clerk in the store, who swiped it through his POS device, keyed in the amount of the transaction and waited for an authorization code to appear. There was apparently a problem with the connection of the POS device to the authorization service. What appeared on the LCD screen of the POS device was a pattern of random LCD segments that looked something like this:
The clerk didn't recognize this as anything other than a valid authorization code, and proceeded to carefully copy this pattern into the space for the authorization code onto the credit card payment slip. Apparently, nobody had told him to expect a series of numbers for the authorization code.
I left the store wondering what other types of mistakes had happened when the store processed credit cards. I doubt that I saw the worst mistake that an untrained person ever made.