But the Stylebook Says...
http://www.theslot.com/style.html

Walsh, Bill
Slot, The
2001

Abstract:

You might think a chapter about how to read a dictionary is a waste of paper, but you'd be wrong. Stylebook entries are designed to be even more explicit in their explanations than dictionary definitions are, but writers and editors still manage to miss the point. When members of the American Copy Editors Society were asked to cite examples of often-misused words, John McIntyre of the Baltimore Sun nominated 'stylebook.' The most common form of stylebook abuse is the use of an affirmative entry as a negative entry. Boneheaded editors see x in the stylebook and decide that means they must never, ever use y. A lot of stylebook entries do work this way, but the authors of the stylebook are giving us a little credit and figuring that we can tell which y they're discouraging. One entry, for example, reads 'spaceship.' This doesn't mean all other words in the language are banned; it means simply that AP does not use 'space ship' as two words.