SE should give Turbine Inc. a call. When they first launched their Lord of the Rings Online mmo , for the first few months there were gold sellers spamming all over the place, even in the in-game mailboxes.

I don't know how they did it, but the dev team had completely annihilated gold spamming during the 5 years I spent playing that game. Never got a gold spam ONCE DURING THAT ENTIRE TIME. It was damn impressive.