Notice: TubeStop was discontinued on December 25, 2012 and is no longer supported.
I’ve updated the TubeStop Firefox extension to work with YouTube videos that have embedding disabled (like this one of Ben Folds covering Elton John). Since TubeStop replaces the auto-playing video with the non-auto-playing embeddable version, these videos were not being properly replaced.
You can install TubeStop from the TubeStop homepage.
What is TubeStop? It’s an extension for Firefox that prevents YouTube videos from automatically playing when you open the page.