[gnat]

"An organization can get surprisingly far with a huge number of bus-factors". So much this.

Some managers see high bus factors as a sign of success: "we are a team of specialists: it's so much faster to give a problem to X than to have Y come up to speed on X's code base."

This, of course, sets X up for (invisible?) pressure not to take holidays or get sick. And because problems don't occur evenly across your code base, chances are that one of your devs gets far more bugs to fix than the others. And because the pressure at your org is to go fast, there WILL be bugs to fix. "Testing is too slow", etc.