Youtube contains a lot of educational material you would not find otherwise. If I wanted to learn sewing on a sewing machine, I would just watch some video tutorials - try that with a book on sewing. Same thing with instructions on how to play instruments. Heck you can even watch videos on how to fix problems with your car engine. Many procedural instructions can't be transported properly via papers or books. It also allows asynchronous video messaging for laymen asking experts stuff which is difficult to get via written text. I bet that youtube will contribute very much to knowledge preservation and distribution in the long term.

I hope that Google look after it a bit better than they've looked after their Usenet archives. Google groups search is a particularly frustrating experience.

I agree that there is some great content on Youtube. Interesting that you mention sewing machines, because that's something I've used and they are particularly helpful. (See also all those other crafting videos; latch-hooking etc.)