I think the main reason why we're seeing such a shift is that in the long run it is easier to ram advertising down people's throats over a video link than it is to get them to click on ads in textual content. The CPM's paid for delivered video ads reflect that, they count those much higher than delivered (but not clicked) text or graphics (even flash) ads.

I don't know... there are also a lot of 'screencasts' coming out from developers. Personally I can't really stand them, for most of the reasons mentioned elsewhere in this thread. The only excuse for them that I could see would be that they'd be easier to put together than a well-written article with appropriate code clippings and images, but I'm skeptical of that.

Yes, and in the case of espn: you didn't think Joe Intosports likes to read (espicially at the evening, it's too much like work).

True enough :) Another big factor is that television / video by default are passive, in other words your brain is in a different mode than when you are reading. A person that is reading is far more likely to see an advertisement for what it is, an interruption of their day and a waste of bandwidth. Television / video consumers are more in the mood for wasting time and will pay attention to almost everything as long as it moves.