In the middle of its biggest growth spurt ever, just before Christmas, Apple fired 800 of its employees for stealing. They were caught grabbing $100 rebates on the iPhones Apple had given them for free.
The impact of this sort of action is pure marketing. It sends a powerful message to every other employee (and eventually the public). Most organizations would waffle, or hesitate at the scale of the firing or try to come up with an excuse for the really really good employees.
There are hundreds of stories you can tell to your staff. Even when you don't try, you're telling a story.