An email links me to a list of video suppliers on YouTube. The source is IPEX, a UK print show with a global reputation growing through LinkedIn.
I am not sure when academic journals and websites will think it normal to include video. There is still a strong print culture and an authority to page after page of text.
But even if video is not part of the book, as promoted by Adobe for PDF or in the new EPUB features launched at the London Book Fair, there is now so much video available that the book has to be designed with that context. Quite when this suits most people is still an open question, but definitely worth asking.