Which "huge vested interests" are you referring to specifically? I can understand that if the Khan academy were to really take off, it'd shake quite a lot of educational institutions. Everything from universities, state-funded schools, teachers unions, the works. And I don't think a lot of them would like that, as I it would appear to the individuals running/manning them that their jobs are on the line.

The reason I say state-funded schools wouldn't like this is because they work on a false premise. Supposedly that education is not free/cheap enough, and that government funding is required to make it work for the masses. You take away that, and public/state schools become glorified daycare so that the parents can stay productive instead of having to babysit their offspring.

One addition: I've just setup a recurring donation to the Khan academy. One small step at proving that society can function without state-coercion.