The New Copyright
"Copyright law gives NBC and other broadcasters the power to deny anyone the use of its content, at least presumptively. If you want to rebroadcast Meet the Press or sell copies on the Internet, you need NBC’s permission. There are exceptions, at least in theory. The law, for example, exempts ‘fair uses’ of copyrighted material from the control of its owner. If a clip is short enough, or if its use is sufficiently transformative or critical, then the law allows its use, whether permission is granted or not.
"In practice, however, the matter isn’t that simple. The costs of defending a fair use right in court – and, more important, the costs if any such defense should fail – make the risk prohibitive for most creators. Defense of fair use could run hundreds of thousands of dollars – several times the budget of a typical documentary. And losing this type of claim could expose the filmmaker to $150,000 in damages for each copyright infringed. In a world in which Fox News sues comedian and author Al Franken for parodying ‘fair and balanced,’ a cautious director can’t be too careful."
Lawrence Lessig. Copyrighting the President. Wired. Aug. 2004.