I usually introduce it to management as "the bus factor" - how many people in this team would it take to be hit by a bus for the team to be completely fucked.

I usually introduce it to management as "the bus factor" - how many people in this team would it take to be hit by a bus for the team to be completely fucked. I'm currently working (and soon leaving) a job like this - there's someone that keeps so many things to themselves that if they were hit by a bus, nobody would be able to deploy anything, etc. which is just unacceptable IMO.