"Khan Academy and its donors may preclude better products from coming along"
I just don't understand this. KA, Udacity, Coursera, Codecademy, MITx, teachontablo.com, this list goes on. I don't see how KA has done anything but prove the possibility of traction. When professors like Thrun and Norvig and investors like Paul Graham, Fred Wilson, and Peter Thiel are excited about the educational space, I believe the students will eventually win. It's no secret that many of the above have been inspired by Sal in one way or another.
The more products competing here, the better education will be. Yelling at Khan Academy because it's "the only thing that [exists]" feels...oddly misplaced.