Like the video said, it's preference. You can say that it makes more sense to have the back and forward buttons and address bar under the tabs so that it's associated with them, and it does. But I think it makes sense to have a function that has the same effect on all tabs to be static. Anyway, as long as they give us the option to choose I don't care. What I want is firefox to give me the option to make the new tab "+" button close the current tab by middle clicking on it. That way I can have the functionality of the good old red x back without losing the new awesome new tab +.