That's an interesting question that should be addressed.
Fan fiction is a form of derivative use.
It also seems to indicate that it is still a violation but the punishment would be less harsh. That's what amounts to plagirism and something you really want to avoid with fan fiction. It seems to indicate that in the future, this differentation between idea and property may lead to fan fiction having I don't know how to word this correctly but less of a legal threat or not as harsh a copyright violation if one at all. More on Fair Use That article makes note of though, the Digital Millineium Act which was created in order to curb the free sharing of music, movies, on-line books etc protected under copyright on the Internet. This document contains, or at least as much as I have been able to acertain from articles about it and my own reading of it, articles that restrict materials that were once protected under the fair use doctrine.