The internet is a very strange place for copyright laws right now, and things are still very much being sorted out with regard to holder rights over audiovisual content streaming and the like, especially when it comes to parodies of copyrighted material.
So, it's no surprise that the Twilight Saga has found itself dead center of a now-resolved case of note and study regarding the Digital Millennium Copyright Act of 1998.
In short, the attached 2009 YouTube spoof called "Buffy vs. Edward" became a battleground of sorts after the video - which combined footage from Twilight with that of Buffy The Vampire Slayer clips to, as the name of the vid suggests, have the two characters go to war with one another - went viral.
It was first subjected to an audiovisual copyright claim by Twilight studio Summit Entertainment (now Lionsgate) which allowed the company to place ads on the videos and receive the profits. The owner itself did not want to do that, so a challenge was issued. The video was later placed under another copyright claim, this time for visual content, and the fight waged on.
Eventually, the dispute was settled, and the video now lives on in original form and place, free of ads per the owner's wishes, but much time, effort and debate went into securing that survival.
You can read the full, fascinating story at Forbes.