The departure of Donald Rumsfeld after the recent Republician US election disaster led to the Guardian to review some of his 'insights' - here is my favourite:
"The message is that there are no knowns. There are things we know that we know. There are known unknowns. That is to say there are things that we now know we don't know. But there are also unknown unknowns. There are things we don't know we don't know."
It's easy to see why KM is so hard to do - especially in the US Department of Defence!