I first encountered this idea in a sci-fi story (I want to say it was one of Peter Watts' "Rifters" novels, but I can't find it now). The idea was that someone trained a neural network to look at live video feeds of passengers moving through a subway station, and control the station's ventilation system. Unfortunately, the movements of individual people were fairly random, whereas the large-scale traffic patterns were extremely regular and periodic. So instead of basing its output on the actual crowd patterns, the neural net decided it was more accurate to look at the hands of an analog clock that happened to be visible through one of its cameras.

All well and good, until the clock stopped working during rush hour, and people started asphyxiating.