My friend John (who works as my property maintenance man) used to work in a major liquor store here in Dallas.
Although he was usually careful to check ID, one Sat. night when they were very busy he let slip a sale to a couple of girls who were pretty close to the appearance of being underage.
Sure enough - it was a sting operation by the police.
John ended up with a class E felony on his record and of course lost his job.