This is Sal here. I wanted to respond directly on the author's page, but they seem to be having a problem taking comments.
The reason why I make history videos is that many people I know (many of whom are quite educated) don't even have a basic scaffold of world events in their minds (or the potential causality between events). Most American high school and college students would find it difficult to give even a summary of the Vietnam War or the Cuban Missile Crisis. Many of these people have sat through years of traditional history classes (taught through state-mandated books by "experts"). Even more worrying is many experts who have taken one side or another of a historical issue and view their viewpoints as facts (this is the tone of most history books).
If the author really watched my videos, he would see that I start most of them telling the listener to be skeptical of anything I tell them or anyone tells them; that no matter how footnoted something is, in the end it is dependent on people's accounts--the people who weren't killed--which are subject to bias (no matter how well-intentioned). Very few history books or professors do this. If anything, they create a false sense of certainty.
As for the "one voice" issue, I don't see how a guy making digestible videos that inform and encourage skepticism (on YouTube where anyone else can do the same) are more dangerous than state-mandated text books. I don't see how lectures that are open for the world to scrutinize (and comment about on YouTube and our site) are more dangerous than a lone teacher or professor who can say whatever they like to their classrooms with no one there to correct or dispute them.
Finally, there is nothing I would like to see more than other teachers/professors/experts adding their voice to the mix. Rather than wasting energy commenting on other people's work with pseudo-intellectual babble, why don't they produce their own videos and post them on YouTube? If someone can produce 20 videos that seem decent and want to do more as part of the Khan Academy, we'll point our audience at them. If our students respond, we'll figure out a way that they can potentially make it a career.
regards, Sal