A lot of people, using intellectual property they don't own, jump to Fair Use as a defense for copyright infringement. Here's why that's a bad idea.
To be fair, most people only use parts of Fair Use as their defense. Those people are caught off guard the most when they are reported, because they didn't take all factors of Fair Use into consideration. Many people also like to use Fair Use as a defense without considering the larger, more important context of copyright law as a whole. When this happens, you're not a victim of abuse by a big, greedy corporation. You're a victim of ignorance, and as we all know, ignorance is not a valid excuse for breaking the law. If you want to use, or create, copyrighted materials, it's your responsibility to understand copyright law.
Digital Arts Instructor