. . . Finally, because the doctrine has vague contours, copyright owners are inclined to interpret it very narrowly, lest it expand by increments.
The result is a systematic overclaiming of copyright, resulting in a misunderstanding of copyright's breadth. Look at the copyright page in virtually any book, or the copyright notice at the beginning of a DVD or VHS film recording. The notice will almost always state that no part of the work can be reproduced without the publisher's (or movie studio's) permission. This is a flat denial of fair use. The reader or viewer who thumbs his nose at the copyright notice risks receiving a threatening letter from the copyright owner. He doesn't know whether he will be sued, and because the fair use doctrine is vague, he may not be altogether confident about the outcome of the suit.
The would-be fair user is likely to be an author, movie director, etc. and he will find that his publisher or studio is a strict copyright policeman. That is, since a publisher worries about expansive fair uses of the books he publishes, he doesn't want to encourage such uses by permitting his own authors to copy from other publishers' works. So you have a whole "law in action" law invented by publishers, including ridiculous rules such as that any quotation of more than two lines of a poem requires a copyright license. . . .