These resources offer general interpretations of copyright law and fair use. Not to be used as legal advice. It seems that there are two ways to make certain you are following fair use: one is through a court ruling in your favor, the other is doing your best to follow fair use and not get sued.
Source: Madrigal, A. C. (2012, March 1). Reading the Privacy Policies You Encounter in a Year Would Take 76 Work Days: So, it's a good thing no one reads them! The Atlantic Monthly. Retrieved from http://www.theatlantic.com/technology/archive/2012/03/reading-the-privacy-policies-you-encounter-in-a-year-would-take-76-work-days/253851/#disqus_thread