In my mind, less and fewer illustrates quite well virtually all of the problems of prescriptivism: the codification of the opinion of some eighteenth-century writer, the disregard for well over a millennium of usage, the insistence on the utility in a superfluous distinction, and the oversimplification of the original rule leading to hypercorrection.
I found a very lovely example of hypercorrection the other day in The New York Times: “The figures are adjusted for one fewer selling day this September than a year ago.” Not even stuffy constructions like “10 items or fewer” make me cringe the way that made me cringe.
No usage or style guide that I know of recommends this usage. In my experience, most guides that enforce the less/fewer distinction grant exceptions when dealing with things like money, distance, or time or when following the word one. And why, exactly, is one an exception? I’m really not sure, but my best guess is that it sounds so strange that even the most strictly logical prescriptivists admit that less must be the correct choice.
Merriam-Webster’s Dictionary of English Usage has an excellent entry on less/fewer, but surprisingly, regarding the “one fewer” issue it says only, “And of course [less] follows one.” Perhaps the use of “one fewer” is so rare that the editors didn’t think to say more about it. Obviously someone should’ve said something to the copy editor at The New York Times.