I just learned the phrase "circus factor" ("If you or someone on your team ran away to join the circus, how stressful would it be for the rest of the team?") and I like it much better than the widely-used phrase "bus factor". https://mercedesbernard.com/speaking/minimize-circus-factor/
@jamey At a job not so long ago, we used "sheep factor", because half of us were living in small villages where shepherds are still plentiful, and we had one person run away to start herding sheep. (He's still herding sheep, and is happier than ever.)
@algernon That's delightful!