Quite interesting. I remember reading somewhere that agents would log into WoW to monitor "terrorist activity". Not sure if they found any though lol.
If few years ago, with the release of the ZG patch, players could catch a disease that basically just drained your HP until, well, you died. It was supposed to be confined to the instance, but an exploit allowed people to take it out into the open world. By "open world", they meant Ironforge, Orgrimmar, etc, during peak hours. As this disease was contagious, hundreds of players' characters started dropping like flies all over the place. Awesome for trolling! Long story short, organisations like the CDC actually studied footage of this to get a better understanding of people's reactions to an epidemic.