So it seems that Florida diners are ordering grouper and getting counterfeits: On Fla. Menus, a Favorite Fish Experiences Identity Theft. I suspect that when the stuff is slathered in sauces, or charred to within an inch of charcoal, diners can't tell the difference anyway.
It all puts me in mind of the story of the lady who went to Zabars in New York and said, “I'd like half a pound of caviar. And make sure it's imported because I can't tell the difference.”