YouTube and other sites like it have an interesting law that they have to deal with, DMCA, which is the Digital Millennium Copyright Act of 1998. This Act give service providers like YouTube protection from copyright infringement liability insofar as they meet specific requirements. One of the largest points for these type of providers is that they have to implement a "notice-and-takedown" system. The requirement that goes along with the "notice-and-takedown" system is that repeat infringers accounts must be canceled.
Congress granted online service providers (like YouTube) certain protections from copyright infringement liability, so long as they meet certain requirements. One requirement of this "DMCA safe harbor" is that online service providers must implement a "notice-and-takedown" system. Another requirement is that YouTube must cancel the accounts of "repeat infringers.
Here is a video about fair use and at about 15 min 30 sec in there is a really interesting point that is made by Lawrence Lessig: it is called Re-examination of the Remix.
Think about it when we use the internet there are rules that are there that we don't even know about. How would you like to be treated like an elementary student having to copy something so that your video can be posted and not taken down. The internet is such useful service but there are many aspects about it that cause problems for users. There are whole processes that are required