Scratch that screencastΒΆ
Uhm, yeah, that last screencast didn't really work out. Sorry. Doesn't work out well on youtube. I think the initial movie was too big and youtube probably introduces too much artifacts. So if someone has the ideal settings (imovie, ishowyou) figured out, please mail me :-) Especially concerning the reasonably big screen area you might want to show (main content area, portlets, etc) and the limited size of youtube and friends.
And a second thing that didn't work: embedding the video. It turns out that you have to add "embed" to the list of custom allowed tags in your site setting's "html filtering" configlet. Some unrelated movie to test out that it works now: