Chilling

The Free Expression Policy Project at the Brennan Center for Justice at NYU offers A Preliminary Report on the Chilling Effects of "Cease and Desist" Letters:

When does copyright control end and "fair use" begin?

Fair use allows students, artists, journalists, and others to borrow and quote from copyrighted material without permission if they are doing it for purposes like commentary, parody, or news reporting. But the contours of this fair use defense to copyright infringement are vague, and in the real world, most disagreements don't get decided in court. Instead, copyright owners - especially corporate ones - send threatening "cease and desist" letters to those they think are violating their copyrights or trademarks. Needless to say, these letters do not advise the recipients that their borrowing might be fair use.