The ideas I've heard?
1.) The tape was made to help the Shaik (sp?), seen with Osama, raise money at home, much like the other tape found was for use in recruitment.
2.) It was made for posterity. To show Osama's greatness and the worthiness of his cause.
3.) Both 1 & 2
4.) This was to be Osama's admission (read as claim to fame). Claiming he did it for the greater good and justifying the actions, before he is caught or captured, and left behind to inspire others.
5.) Produced by Dreamworks Studios. The inaudible sections and bad audio used to add authenticity.
I personally believe in all, but #5. If #5 were true, it would have already grossed $200 million.
