When you should fire your most irreplaceable team members (opens in new tab)

On the contrary. This view assumes that replacing employees is about the hardest thing you have to do. Good people are extremely rare. So to mitigate the problem, and also to promote intellectual cross pollination within the organization, it's a very good idea to make sure everyone remembers to document what they know by default. There's no need to assume this means extra work - it just means you divide your time differently, giving more priority to communicating what you know. As an _employee_ I always strove to do just that - volunteer to document and spread on whatever I brought with me into the organization, and everything I picked up along the way, too. I saw this not as a chore but as a an opportunity to share, influence and also have less of a headache when the time eventually comes to move on to the next adventure.

Yup. But it's a goal to strive to. Nobody's proposing people spend their entire day documenting, but if they remember to document decisions/knowledge by default they mitigate the problem. Besides, who said it's a good thing to have one person with 10 years of very specific, undocumented domain expertise? Sure, in rare cases it's some outlier guru. Sometimes you have PhDs who spent 10 years becoming domain experts and you can hardly expect them to be able to serialize it all into the company wiki. That happens. But I'd bet that in most cases these are just people who positioned themselves into a cozy role, guaranteeing you can never let them go. These are liabilities, not assets.