MoveOn.bored,

 If you lock someone up and throw away the key they will die shortly from lack of food and/or water.  Then you would have a rotting corpse to dispose up but unfortunately no key to the door.  You would increase costs by breaking down the down and replacing it or by a new key.  Of course, someone might find the key you suggest get thrown away, and then they could let the locked in person free, no?

I doubt this person will be "slapped on the hand", since we save that special treatment for the most powerful and influential among us.