Too often, excuses from a site like http://www.yourlogicalfallacyis.com sums up why an organization doesn't maintain enough documentation of their business and the knowledge contained with it, and it's free to just walk out the door.
I've observed with clients while systemizing their businesses: In the long run in those who don't keep it a priority to document, improve and transfer their knowledge capital regularly, peak out, stall and fade.
By failing to bake into the bread of their culture that understanding and sharing the why to do things a certain way.. maintaining their competitive advantage, they inevitably are exposed to becoming less effective, productive, efficient, ultimately welcoming a culture of accepting less and less.
It's also probably worth noting that I'm not talking about creating a mistake manual, but rather a why manual that helps teach the mindset that creates the types of mindset required to make decisions to grow the business
Businesses that become institutions do so with cultivating a a 50 to 100 year mindset, but few have a 10 year mindset to take what we do today and make sure it's happening while we find the next way to grow.
A markdown based wiki would be a decent start, but I still overall feel like this is an unsolved problem.
Perhaps a wiki that allows pulling in "snippets" from linked pages could help.
As a programmer, wiki syntax seemed pretty obvious to me. But it was a block for some of the non-coders.