It's a fascinating movie. I've heard that the reason the makers did not give themselves credit anywhere in the movie is that they were threatened and need to hide. That's apparently also the reason why there's no interactive tool being added to the website (unlike promissed) hence their site is not getting any facelifts anymore. If you do a little search on Zeitgeist, you will find places where the movie and its effects on society are discussed - which pretty much takes over for where Zeitgeist makes (had to) take off:
Zeitgeist The Movie - The North American Union??? WTF
