Here's an account by a retired engineer of what happened when his old company wanted to streamline a process in the factory where he used to work.
People only knew how to keep the factory going from one day to the next, but all the documentation was lost-- the factory had been sold a couple of times, and efforts at digitization caused more to get lost. Even the name of the factory had been lost.
Fortunately, engineers keep more documentation than their bosses allow them to. (Trade secrets!) And they don't throw the documentation away just because they've retired.
I've been concerned about infrastructure neglect for a while, and this makes me more concerned. On the other hand, instead of just viewing with alarm, I'd like to view with quantified alarm, and I don't have the foggiest on how to quantify the risks.
Also, some of the information loss is a result of a search for efficiency. How can you tell when you're leaving something important out?