I think youtube has a special agreement with google because they are premium publishers. And they have text content since many videos have comment and user's description.
Why can't you put Google ads on a "funny videos website"? Content is content, and as long as the content isn't violating google's TOS, I don't see why it's prohibited.
i thought that your not allowed to put ads on pages where there is no content, basically you not allowed to attract traffic to a page with just ads. I think videos are just fine because they are content.
yes there's this part in adsense policy "Copyrighted Material In order to avoid associations with copyright claims, website publishers may not display Google ads on web pages with MP3, Video, News Groups, and Image Results." But there are many ways to read it and if they're premium publishers anyway they don't have the same policies.