Beautifully put - I nominate this as the official summary of the subthread. It's the reason why we need to pad time estimates for projects and leave early to ca

Beautifully put - I nominate this as the official summary of the subthread. It's the reason why we need to pad time estimates for projects and leave early to catch trains, even when we can't think of any likely reason for delay - the sum of all unlikely reasons can cross the threshold into "likely". So it's quite correct to say "unlikely events happen all the time".