I have the Black MacBook 13.3" (which may not have anything to do with this issues). Whenever I view YouTube/QuickTime/ and most DVD's they are not full screen. Even though I set it to full screen.. it is kind of a rectangle shape (up and down) and it does give me the fulls screen look on either my 27" TV or 13.3 screen.
Here is a screenshot.. not the best picture, but gives you an idea of what I mean:
Here is a screenshot.. not the best picture, but gives you an idea of what I mean: