and i was like, "go on..."
In contrast, with a Redundant Array of Insolvent Banks, there is a very high correlation between bank failures -- but you're saved by the FDIC per-bank insurance limit. You're not modelling your risk based on known probability distributions; you're eliminating your risk entirely (at least as long as you trust the FDIC).
To (over?)extend the analogy further, there's always the possibility of a controller failure.