How Effective Are Documentary Films In Changing The World?

I watched a pretty thrilling documentary this year called THE COVE, and by thrilling I mean that literally, it was like a spy/mission impossible format where a group of Americans went to Taiji in Japan to stop the killing of Dolphins that’s been done in that town for years. In my review, I didn’t completely praise the documentary. Don’t get me wrong, I’m against killing dolphins but it seems hypocritical to go to your neighbor to tell them what to do when in our own backyard, hunting is still allowed in many states. Let’s say if a Japanese likes to eat Dolphin meat over there, who am I to tell him to stop when I myself am eating beef and chicken over here. And if the activists are so into saving Dolphins, then why not save Tuna and protest against killing Salmons too?!

Dolphin hero Ric O’Barry blogged at takepart.com recently and discovered that his documentary THE COVE has made a significant impact in Taiji…

Today is September 1st, the first day of the dolphin slaughter season in Japan. But when I arrived today by bus from Kansai Airport with media representatives from all over the world, the notorious Cove from the movie was empty. There were no dolphin killers in sight.
And as I was talking with the police, as the international journalists stood around listening, suddenly a camera crew arrived from Japan! And then another! And then still another!
You have to understand that this is SO IMPORTANT. These TV stations have REFUSED to cover the story in Taiji for years and years. NOW, for the first time, they have shown up, with cameras rolling. The head policeman talking with me even said, for the cameras, that the police are not there to support the dolphin killing fishermen.

Did Morgan Spurlock‘s Super Size Me stop people from eating unhealthy food or stop fast food chain from giving out junks? Because last I checked, America is still an obese nation.
Did Davis Guggenheim‘s An Inconvenient Truth raise public awareness on global warming or did it just raise the number of celebrities who want to be humanitarians and environmentalists for publicity purposes?
Did Michael Moore‘s Sicko manage to get U.S. government to revamp its medicare?
Did Ben Stein‘s Expelled stop the persecution of scientists who believe in Intelligent Design?

I’m not saying there shouldn’t be any more outspoken Documentary films to be made but… When was the last time a documentary actually compelled you to become an activist?
Or is it just like watching the news on TV where afterward you get back to eating your dinner, not remembering you’ve watched anything at all?
Is it more effective to have a documentary about a genocide in Rwanda or a feature film about it like Hotel Rwanda?
What do you think documentary filmmakers should do more to get the message across and actually make an impact?