World of Warcraft gold farmers and spammers have always been quite the problem. There have been multiple investigations, videos and documentaries on the lives of farmers. I bring them up now because with the release of the expansion they seem to have made a comeback. Obviously with the release of new content people want to get ahead and this is why.
I play on a rather popular server so the price of newer items is mind blowing. Farmers actually help to bring the economy of my server to a more reasonable average. While they are annoying when you are trying to make money, they tend to just blend into the background. While selling gold is against Blizzard policy, it does help to balance the system.