D'oh! or is it Duh!

From Instapundit:

GUN REGISTRATION: Such a bad idea that even the Canadians are scrapping it. "One former Mountie called the registry 'totally useless' because criminals don't register their guns." Too bad they didn't figure that out a few billion dollars ago, but at least it's an object lesson for the United States.

Who'd 'a' thought?