If you're more familiar with music documentaries, you've probably come across this one. Directed by Brett Gaylor, 'Rip! A Remix Manifesto', came out back in 2008. It had been in the process of making for over six years. Nevertheless, I think the doco tackles the matter of copyright laws in a way that won't be outdated as fast. Even though, the mash-up producer Girl Talk, one of the centric characters in the movie, would say that in retrospect, these problems will simply seem nonsensical.
The Creative Commons licensed movie is a collaborative remix itself, drawing from hundreds of contributors and making it the 'world's first open source documentary'. Enjoy learning about sampling, remixes, mash-ups, laws regarding them as well as the music industry that directs the show!