Interesting idea, I like the concepts... one thing that stands out right off the bat though for me is if it's going to be all video, we should try and make some recommendations on the best way to do video walk-throughs. For example, you've got several points there describing how to get the best video quality, how to make sure things are always in focus, use a default firmware install whenever possible, etc. Personally if I was to do some demos for this type of thing I would use x11Vnc in combination with something like Adobe Captivate:
http://www.adobe.com/products/captivate/
Now, not saying that everyone should go out and buy that software, but the whole point is that rather than "shooting a video", Captivate allows you to make a dynamic animation or video of your screen, along with comments and things describing what you're doing after the fact. Now if somebody could suggest an open source app that does relatively the same thing then I think that would be a much, much better way to go as it eliminates many of the "gotchas" you describe while at the same time. Again, viability here varies, as really it makes more sense to have somebody like a "debmaster" be "tutorial master" to help get people who want to contribute to figure out how the best ways to go about it are (but not have to be responsible for doing all the work themselves of course!), but that might not be entirely possible... even if we just had a group of people who had done a few and were willing to volunteer from time to time to make up these tuts to demonstrate things that others suggested I think that would help with the consistency factor...

Bringing up my second point there... to be successful I think there'd need to be a very easy and open way of users requesting walkthroughs for things not covered. I write for a web developer community website, and one of our biggest draws for users is that we actively spend time in the forums asking "what else do you guys want to learn?", in addition to showing off the cool things we do on our own. I think that would go a long way to helping make the Maemo experience far beyond any other mobile platform out there...

Just my thoughts anyways!