While he wasn't giving away any numbers, Mythic's lead Warhammer Online designer, Mark Jacobs, said recently in a blog that gold farmers have offered him huge bribes to allow them to ply their ill-gotten ingots.
Here is the direct quote from his blog: "BTW, for those who might be tempted to think that we are doing this so we could offer our own service or because we do make money off their boxes (traditionally, gold sellers will quickly shift to buddy disks and free trials though to lower their costs) let me tell you this. I’ve been offered “a piece of the action” both personally and corporately in the past if I will either turn a blind eye or help them in their actions. This would have netted me and/or Mythic a very, very tidy sum, far more than we would see from box sales. My answer was and always will remain the same: Go to hell."
In the rest of the blog, Mark Jacobs just says "no thanks" to all the gold farmers spammin' it up.
Makes me wonder about some other MMORPGs that I've played, that seemed to be stuffed to the gills with gold farmers -- were those studios taking bribes, perhaps? It seems like it would be easy enough to report and ban gold farmers spamming chat channels -- but many MMORPGS seems to have trouble doing so.
The true size of the gold farming (and power leveling) industry is unknown. But one initial study that tried to gauge the size of this industry believed that 400,000 people where employed gold farming, racking in profits of over 500 million USD (which seems absolutely incredible.)
The vast majority of gold farming is done in China. A recent trend has also shown that Chinese gold farmers have been increasingly out-sourcing their work to even poorer countries, such as Vietnam and Cambodia.