What Happens When One of Your Coworkers Dies 
This has happened in my experience before, and it is one of the strongest reasons for good source control that is infrequently considered.  It was a tragedy when a very wonderful and dear researcher in our group died suddenly, especially to his three children and wife that he left behind.  It was also a great loss as well that we could never recover some key bits of source code from his computer, and that a very promising cancer drug trial was derailed because we couldn't articulate why the compounds were chosen for study in the first place.<p>He died of a heart attack at age 42 after pulling three 90+ hour weeks.  It completely changed my attitude towards work.  May he rest in peace.