Horse's Head given by the Horse's A . . .
There is nothing obvious about Whittington's background to suggest that he might be regarded as disposable. But according to a Slate article, the protocols of good hunting were not followed (http://www.slate.com/id/2136206/), which is curious since hunters and other gunsmen tend to be anally safety-conscious.
A comment at the Nation website gives some information to corroborate Saunders. Apparently, "Harry Whittington" was Libby's Secret Service codename . According to an unnamed EMT worker at the scene, Cheney was concerned about leaks. If so, he had already made up his mind not to give out information at that time, and, if Saunders is correct, wanted to make it look a little suspicious to intimidate Libby further. (http://www.thenation.com/blogs/notion?bid=15&pid=59468 )
All extremely speculative, to be sure. But as Johnny's post ("Besides All That Mr. Whittington, How Was The Safari?") points out, the official version doesn't make sense, and is most likely false.