In no particular order:

1. The ability to disable comments exists

2. The ability to disable embedding exists

3. The ability to disable ratings exists

4. The ability to disable video replies exists

5. The ability to pre-emptively censor messages from anyone not on your friends list exists

6. Morons without the most basic understanding of grammar or spelling write most of the comments

7. "Most viewed" rankings and lack of sifting mechanism rewards videos that lie about their content in the title

8. Legal videos get removed for no good reason (e.g., the entire XenuTV account was deleted)

9. Crappy softcore-porn videos, and other shit posing as softcore porn with 1 frame of it in the right position to be thumbnailed, dominate the top video list. It's not even good softcore porn.

10. Shitty videos made unrehearsed without a script that consist of at least 75% "um".