While I'm not sure of the math, I enjoyed this quote from Mobs, Messiahs, and Markets: Surviving the Public Spectacle in Finance and Politics:
Ignorance increases the square of the distance from a given event, so the odds that things won't work out the way you expect must be multiplied by the squares of all the intervening events.
It reminded me of what Peter Bevelin Wrote in Seeking Wisdom:
The more independent steps that are involved in achieving a scenarios, the more opportunities for failure and the less likely it is that the scenario will happen. We often underestimate the number of steps, people, and decisions involved.
Add to this that we often forget that the reliability of a system is a function of the whole system. The weakest link sets the upper limit for the whole chain.