YouTube already has some pretty strict rules and conditions stated right up front which you have to agree to before you can upload any content. Despite such guidelines, a lot of people still put up videos with copyrights that are owned by entertainment companies or smaller, private entities.
Some people violate these terms accidentally, of course, while others are not so innocent. Regardless of which group you belong to, YouTube's not taking any excuses.
If someone flags your video for copyright violations, then YouTube's sending you straight to Copyright School, where you'll have to watch a copyright tutorial and then pass a quiz to show that you understand what you just saw.
YouTube is also providing you with enough materials to prevent this from happening by way of their Copyright Help Center and by releasing a new tutorial on copyright featuring your favorite Happy Tree Friends characters in a not-so-bloody episode:
(I'd just like to note that the video has received 757 likes as opposed to 4,052 dislikes as of April 17, 2011. I wonder what users are trying to say about the video, since comments have been disabled by YouTube.)
If you're a frequent YouTube user, remember that their policy states that three uncontested copyright notifications will result in your account getting suspended. However, they're also making several notable revisions in this rule.
You can read all about YouTube's updated copyright policies here: YouTube Blog