Understanding 'Mean Time Between Failure': Coupling, Complexity and Normal Accidents

In 1984, Charles Perrow wrote an amazing book titled Normal Accidents: Living with High Risk Technologies. In it he observed that system accidents can be the result of one big failure, but most often are caused by the unexpected interactions between failures of multiple components.
In other words, complex systems whose components are tightly integrated typically fail through the culmination of multiple components failing and interacting in unexpected ways. For example, it's very rare that a plane has a wing fall off mid-flight. It's far more likely that several component failures interact in unpredictable ways that, when combined, cause a catastrophe.