1. Corrupted Blood – World of Warcraft
In 2005, an event known as the “Corrupted Blood Incident” erupted in World of Warcraft after players discovered that a debuff spell cast by Hakkar in the raid dungeon of Zul’gurub, which caused players to lose health over time, would work outside of the dungeon for which it was intended.
Though originally intended to only last a few seconds, and only within the dungeon, the debuff spread to other characters within the game’s most populated zones like Orgrimmar, Ironforge and Stormwind City—causing players who caught the debuff to either flee the area, thus spreading it to even more players with whom they came into contact with, or deliberately infect others.
The event inspired scientists to look at the game’s virtual world and served as a new place to conduct research on how people behaved during the event.