The Basics of
Fair Use
Copyright owners have sued and probably will continue to sue individuals.
The penalties for infringement can be very harsh: a court can award up to $100,000 for each separate act of "willful infringement." Willful infringement means that you knew you were infringing and you did it anyway. If you don't know that you are infringing, you still may be liable for damages - only the amount of the award will be affected. A Court may also award attorneys' fees to a party who has to sue to stop or has suffered from an infringement.
A court may refuse to award any damages at all if it so chooses, even if the copying at issue was not a fair use. Such is permitted only with the good faith fair use defense [17 USC 504(c)(2)]. It only applies if the person who copied material reasonably believed that what he or she did was a fair use.
The copyright law itself recognizes several statutory categories of fair use, but those categories are not "bright-line" tests. There remain much gray area even under the listed categories. Because of this ambiguity, it is dangerous to ever believe you are "safe" and the best advise is to ask for written permission whenever possible.
The United States Copyright law of 1976 [17 USC § 107] says:
Notwithstanding the provisions of sections 106 and 106A [17 USC sects 106, 106A] the fair use of a copyrighted work, including such use by reproduction in copies or phonorecords or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright. In determining whether the use made of a work in any particular case is a fair use the factors to be considered shall include--
(1) the purpose and character of the use, including whether such use is of a commercial nature or is for nonprofit educational purposes;
(2) the nature of the copyrighted work;
(3) the amount and substantiality of the portion used in relation to the copyrighted work as a whole; and
(4) the effect of the use upon the potential market for or value of the copyrighted work.
The fact that a work is unpublished shall not itself bar a finding of fair use if such finding is made upon consideration of all the above factors.
The United States Supreme Court, permitted the "2 Live Crew" usage of the song "Pretty Woman" and held that under certain circumstances even commercial usage may fall within the protection of the "fair use" provisions of the statute. Parody or use which alters the material into a new artistic expression may be permitted. DON'T bet on it though.
Copyright and Fair Use are difficult concepts even for judges and attorneys. Play it safe, get written permission or create new works.