Found a really interesting article on the Wired blog a few days ago.
Nick Haley, a huge Apple fan, posted his version of an iPod Touch 30 second TV spot. He used footage from the web and found a song that he thought fit well with the video and then posted it to YouTube where it quickly gained over 400,000 views.
It turns out that Chiat/Day and Apple felt the same. After seeing the spot on YouTube, Apple contacted Nick and flew him to their San Franscisco offices. At the offices, he re-created his spot in HD and Apple then purchased prime time airspace during the World Series to air the spot.
Many companies would have simply called the lawyers on someone like this, but Apple is different. A sign of a great brand is to let brand enthuasists create - and reward them for it.