Back in the 1960s, several people made a living by listening to elevator talk in Wall Street high-rises, selling what they heard, and/or trading on it. Brokerage firms finally wised up and issued "no shop talk in elevators" ukases.
In another interesting case, an engineer at a computer manufacturer in a Southwestern state (yes, that one), made a small killing by trading options after correctly surmising that management's assurances of no layoffs were false. Poor bastard, not only did he have to give up his trading gains, but he was laid off. And did a short stint at Club Fed. A terrible injustice, IMHO.