This is a fascinating academic study of gold farming networks in EverQuest2. I am sure someone is doing something similar for WoW. I love this kind of stuff. These virtual worlds are not just fantasy worlds, the fact that humans are the primary characters makes them into fascinating real-world models for various behaviors.
Recall that MMORPGs have also been used to model disease epidemiology – for example, the “Corrupted Blood” in World of Warcraft which got published in Lancet!