The World of Warcraft Community Site (thanks Scott) describes the actions taken by Blizzard against World of Wacraft cheaters in the month of November, when they busted out the banning stick and whacked some 105,000 accounts and removed more than 12 million gold pieces from the economy that were the product of cheating and gold farming:

In our continued efforts to combat cheating in World of Warcraft, more than 105,000 accounts were closed and over 12 million gold was removed from the game economies in Europe, Korea, and the US in the month of November. The closed accounts were associated with activities that violate World of Warcraft's Terms of Use, such as using third-party programs that allow cheating, and farming gold and items. These types of activities can severely impact the economy of a realm and the overall game enjoyment for all players.

We will continue to aggressively monitor all World of Warcraft realms in order to protect the service and its players from the harmful effects of cheating. Please note that selling World of Warcraft content, such as gold, items, and characters, can result in a permanent ban of the involved accounts from World of Warcraft.

Many account closures come as the direct result of tips reported to our GMs in game or emailed to our Hacks Team by legitimate World of Warcraft players. If you suspect that a World of Warcraft player is using an illegal third-party program to farm gold or items, or is otherwise violating our Terms of Use, please report the suspected infraction via one of the means listed above. All reports will be investigated, and those that prove false will not result in corrective action.