Originally Posted by Peter (IMC)

However, the page the video is in also needs to be optimized. I don't know (yet) how much it helps to use the bits of technical options to indicate the content of the video, but you can be pretty sure that information that´s not visible to the user gets little attention. (just think of meta keyword tags, stuff that´s not visible to the users gets abused and is for that reason not that useful to a search engine.)