+1 for libraries. It's funny that on HN, where people constantly insist that text is a faster way to convey information, opening a history book is not even considered.
To me, it goes back to the goal of the Khan academy: is this meant for pop culture consumption, or more in-depth knowledge?
How does reading the diary of Ann Frank compare to Khan's video?
There's a lot to be said for learning something in multiple passes. A fifteen-minute overview video can give a vague notion of what happened when, and lay the ground work for more detail later -- as well as, perhaps, piquing a student's interest. There aren't that many students who will voluntarily go read through a history book. There are considerably more who will watch a 15-minute history overview video, which may make them more likely to study more history later.
So, watch a video, read a book, read a bunch of books. None of this stuff is mutually exclusive. Rather, I would say its complementary.
To me, it goes back to the goal of the Khan academy: is this meant for pop culture consumption, or more in-depth knowledge?
How does reading the diary of Ann Frank compare to Khan's video?