Unfortunately, he does not explain what a Bolshevik
is nor how or why the Bolsheviks overthrew the Russian
empire, nor why it matters but no dilly-dallying, just
fast forward and bingo...
This is a limitation of the 1-way set in stone nature of video. It could be addressed by augmenting the lecture with an interface similar to an interactive-movie-game at the arcades circa 1993 called Dragon's Lair (http://en.wikipedia.org/wiki/Dragons_Lair). A concept similar to "pick your own adventure" books but with video.
For instance, if some lecture L is about ideas A, B, C, D, and there is another lecture B+ in the library that specifically targets B in detail, then there could be an option presented to the user around the timestamp B to divert to B+ in depth, then come back to C. The important part is that the material is relevant as decided by the user. If they decide B+ isn't what they wanted, they could cut right back to C immediately.
For instance, if some lecture L is about ideas A, B, C, D, and there is another lecture B+ in the library that specifically targets B in detail, then there could be an option presented to the user around the timestamp B to divert to B+ in depth, then come back to C. The important part is that the material is relevant as decided by the user. If they decide B+ isn't what they wanted, they could cut right back to C immediately.