convincing people to edit the official documentation

Awhile ago I read a blog post by Emma that could use some discussion here. It's about herding cats towards editing the projects sources instead of seemingly random locations throughout the world. Sort of.

Documentation: please help fix what's already there
- http://www.emmajane.net/node/927

This topic could easily grow into a monster because so many other factors are at play here. Like, why do people contribute to Open Source? How and why is this idea intimidating? Do contributions feel too anonymous, restricting, difficult, boring... when compared to, let's say, a personal blog post? Why do people provide conference talks (and slides) but not help with documentation? How can the "lack of time" excuse be remedied?

I'm having a difficult time narrowing the scope so hope others here can better describe this topic and help define a plan for tacking it.