[dionysiac]

For those interested, "The (Mis)Behavior of Markets" by Benoit Mandelbrot and Richard Hudson examines, among many other things, the 1987 "Black Monday" event. Mandelbrot theorizes that sudden, disproportionate events such as these may be much more common than today's models and distributions predict. It's a great, accessible read even for those not mathematically inclined.

[lutorm]

Sounds like a "Black Swan".

[marcamillion]

A black swan is an unanticipated event (typically grounded in some fundamentals) - not an error of judgement or algorithm.

[wglb]

But to the extent that judgement and algorithms inform and are informed by our anticipation, it is very much that.