I've tried using the youtube shortcode without success. So I set up a test web site yesterday with the default theme 2011 at http://locutorium.com/wp2010/ - (I should have called the site wp2011) to which I added no plugins and no new pages or anything else. All I have done is to add some additional code to the one and only post page.
The shortcode that I added for YouTube is this - [youtube=http://www.youtube.com/watch?v=OWfksMD4PAg] which shows up on the page completely uninterpreted and no video is played.
I've also added some images and the gallery shortcode [gallery] to prove that shortcodes are being recognised and do work.
Perhaps this shortcode doesn't function on self-hosted WordPress sites - any ideas anyone?