http://arstechnica.com/news.ars/post/20060324-6459.html
I fail to see how it's against the rules, really. If they want to waste their time farming gold, let them. They paid their $15/mo, what's wrong with them making some profit off of the game?
They don't mean actual 'farming' of gold. When people say 'farmer' in WoW, it means chinese guy who plays all day, and sells it to a company. This is exactly how it works:
Brand new server, the first people to level 60 are the farmers and the ones being powerleveled.
More people begin leveling up, and the need for money increases. The ones that don't want to waste their time working for money, go buy, say, 2000 gold for $120, this then making them have an overwhelmingly un-cared for amount of money that they'll be willing to waste on something expensive that they need. On every server, everyone knows there are gold buyers, this brings out people who play the auction house, generally what this is is buying low, selling for an absurd amount higher, hoping a goldbuyer wants it, completely excluding others who work for their money.
So then the only way to make money is playing the AH, therefore making more thinks too expensive to people who actually get their money properly.
Generally, banning gold farmers is perfectly fine with me, if they're gone, our server's economy goes to a normal state, instead of everyone ripping off eachother and something such as a Widowmaker not being worth 400 gold.