So, (asking for a friend, obviously) if you can print your own codes, then what is stopping someone sneaking their own codes into a large shop, sticking them all over the place, with the purchase money going straight into a dodgy off-shore account?
Well, there we go. I've had one on my phone and never used it, because I didn't know what it was for. But this morning, the first one of these things I see is gonna get zapped!