With respect to the Khan Academy, it would be interesting to see tools that provide a kind of interactive exchange of preconceived ideas and then helping to break them down. Having tests after the exchange would then help provide great metrics on the retention and understanding of the subject.
In any case, 1veritasium has at least provided an thoughtful response to the Khan Academy. He recognizes a good thing but provide some nice constructive criticism that could certainly improve what the Khan Academy already could offer. So as someone who enjoys Sal's videos, this idea gets a +1 from me... You know, as just some random person on the Internet ;-).