For clarity, you retain all of your ownership rights in your User Submissions. However, by submitting User Submissions to YouTube, you hereby grant YouTube a worldwide, non-exclusive, royalty-free, sublicenseable and transferable license to use, reproduce, distribute, prepare derivative works of, display, and perform the User Submissions in connection with the YouTube Website and YouTube's (and its successors' and affiliates') business, including without limitation for promoting and redistributing part or all of the YouTube Website (and derivative works thereof) in any media formats and through any media channels. You also hereby grant each user of the YouTube Website a non-exclusive license to access your User Submissions through the Website, and to use, reproduce, distribute, display and perform such User Submissions as permitted through the functionality of the Website and under these Terms of Service. The above licenses granted by you in User Videos terminate within a commercially reasonable time after you remove or delete your User Videos from the YouTube Service. You understand and agree, however, that YouTube may retain, but not display, distribute, or perform, server copies of User Submissions that have been removed or deleted. The above licenses granted by you in User Comments are perpetual and irrevocable.
(Section 6, Paragraph C)
So there you have it. They can do whatever they want with your work, but it's non-exclusive, so you can still do whatever you want. If you remove your video, they can still keep a copy, but they can't use it anymore. Interestingly, they have a Copyright page within their Help Center, but it doesn't mention this.
You agree that: (i) the YouTube Website shall be deemed solely based in California; and (ii) the YouTube Website shall be deemed a passive website that does not give rise to personal jurisdiction over YouTube, either specific or general, in jurisdictions other than California. These Terms of Service shall be governed by the internal substantive laws of the State of California, without respect to its conflict of laws principles. Any claim or dispute between you and YouTube that arises in whole or in part from the YouTube Website shall be decided exclusively by a court of competent jurisdiction located in San Mateo County, California.