I have been curious why everyone was so gungho to declare this video legitimate. Personally I found it dubious on it's face. (pun intended)
All References to Current Events Are Made During Video Freeze.
Osama Bin Laden's widely publicized video address to the American people has a peculiarity that casts serious doubt on its authenticity: the video freezes at about 1 minute and 36 seconds, and motion only resumes again at 12:30. The video then freezes again at 14:02 remains frozen until the end. All references to current events, such as the 62nd anniversary of the U.S. atomic bombing of Japan, and Sarkozy and Brown being the leaders of France and the UK, respectively, occur when the video is frozen! The words spoken when the video is in motion contain no references to contemporary events and could have been (and likely were) made before the U.S. invasion of Iraq.
The audio track does appear to be in the voice of a single speaker. What I suspect was done is that an older, unreleased video was dubbed over for this release, with the video frozen when the audio track departed from that of the original video.