I have a suggestion for supermarkets. I'm sure they'll ignore the suggestion, but I think it's a very good idea:
Before anyone can take a basket, they are required to count to 20. After that, if they have more than 20 items in their basket when they go through the 20 item, or less, line, a trapdoor opens and they're whisked away (in a tube like at the bank) to the place where they first received their basket.
Of course, this would need to be videotaped so their surprised expression could be placed on the evening news for everyone to see.