wrong entrees?

An interesting question pondered by Frank Bruni is The Diner's Journal today:
"What’s the protocol when the restaurant prepares the wrong entree for one of the diners? Everyone else at table has been served what they ordered; one person has been served the wrong and unacceptable dish".

I liked the comments more than the 'solution'. Other than food allergies and vegetarianism, I find it hard to believe that substitutes are so unpalatable.

Link.