"Stupidity should be painful" is a sticker placed on the laptop of a friend. At first we simply laughed about it and went on with our lives. But then it sank in that stupidity is already painful, just witness the Darwin Awards. A truly stupid person will eventually pay dearly for his/her lack of mental awareness.
I think we have all occasionally succumbed to a moment of "stupidity." Most people will simply chalk it up to a learning experience and move on with their lives. The truly stupid will not realize how narrow an escape they have had and may even repeat the stupid action. It is the repeatedly stupid people that will end up as a Darwin candidate.