I specifically don't like the idea of annotations rather than editing, because annotations expand and diffuse the literature rather than distilling it to excellent concise articles. In particular, annotations only address two of my six motivations (#4 and #6).
Within the hard sciences, what do you think annotation accomplishes that can't be accomplished through good editing?
> Nothing is going to replace the paper,
Ahh, a defeatist. You may say I'm a dreamer...
But seriously, I think this is a much more realistic goal than Wikipedia and ArXiv looked like when they were launched.