For clarity, you retain all of your ownership rights in your User Submissions. However, by submitting the 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 successor's) 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, prepare derivative works of, display and perform such User Submissions as permitted through the functionality of the Website and under these Terms of Service. The foregoing license granted by you terminates once you remove or delete a User Submission from the YouTube Website.
Hopefully this clarifies matters and puts any unrest at ease about who owns the rights to your videos on YouTube. YOU own the rights to your videos.
The YouTube Team