I know some people (a Sondheim reference) who think that ANY non-fiction movie is a documentary...no matter what it's about or the viewpoint it takes. 
Hence "reality tv" that people think are documentaries when there's very little reality about it. And those "sensational" docs that HBO does are pretty ridiculous. ("Hookers at The Point"?)
I am often asked about what I consider to be real documentaries, and at what point do they cross over into propaganda. I jokingly say that a film becomes propaganda when it espouses a viewpoint that I don't agree with.
I don't look at Michael Moore's films as documentaries, but more as editorials. There are very few objective documentaries, because as soon as you make an edit, you are controlling the flow of information and imposing your viewpoint upon it. But I think that's one of the things that makes the film interesting... the viewpoint of the filmmaker, as opposed to just throwing out all the information and letting the viewer try to sort it out for themselves.
Thomas Edison's early films (some of which we used in Sacco and Vanzetti) were about as pure as you can get...just setting up a camera and recording everyday action as it happens. That was probably interesting back then but now people want stories, and many documentaries are constructed with a story arc in mind, similar to a scripted drama.
I like Alan Berliner, whom I mentioned earlier, because he has taken an experimental approach and since the film is about some aspect of his life, he can be as manipulative as he wants to be. I wouldn't call his films documentaries as much as essays.
The Internationale is pretty straightforward in that we weren't trying to hammer home an agenda, it really is just the history of the song and how it has impacted people's lives.
I liked the Al Gore film, but there's another documentary on global warming that is far more objective and very well done called "Too Hot Not To Handle". This aired on HBO (they do support good stuff, too!) and was a straightforward "just the facts, ma'am" approach to the topic. They used the song "Dear World", which I had never heard before, over their opening titles. An inspired choice!
Another film on global warming (Greg worked on this one) is called "Everything's Cool". This is about people's refusal to acknowledge that it's a very real threat, and is really well done. It will be going to Sundance and probably end up on HBO, too. Greg can be glimpsed in one scene, miking up Heidi the climatologist at the Weather Channel.
But now that distributors and filmmakers realize that there is a market for documentaries, I've noticed that there is much more crap to wade through to find the good stuff. And it seems that the people who win awards for their films are the ones that put themselves most at risk while shooting, not films that are particularly well-made.
I love working on documentaries, though. It's like continuing education for me, and I have learned so much about topics I never would have, otherwise.
