Remove CoD. It's a Privilage that gets Exploited too often. CoD wasn't in the game for the longest time and there was not scam mailers. Remove CoD and Remove the Scammers.

Remove Money Transfers thru the Mail except from Same Account, Auction House Sales and Kinships.

Make Cash only Tradeable To or From Kinship Mates. Kinships are much easier to keep track of. Make Leaving a Kinship a have a 15 day Cooldown, this way Turbine can attach a tracker to the accounts for large cash transfers and will definately slow down Gold Farmers. You can argue with well the Gold Buyers would simply stay in that Kinship. Fine, but Dev's or players whom hunter Gold Buyers and Sellers will be able to get into one of these Kinships and report the activities. Ban the whole Kinship.

Make Buddy Accounts Unable to Transfer Cash. You can still help your buddy with items just not cash.

Remove the Ability to easily trade the Cash and the Farmers have no way to control the flow. You can go one step further and anything over 1 G in Trade Requires a GM to OK the transfer ..... Call it a Petition to Trade Cash. Yep that would be a FullTime Job for a Group of GM's but it would also enable the GM's to track the cash.

Put a 100% Tax on Mailing Cash. Send 1G costs another 1G to Mail. Expensive Stamps.

Anyone arguing with this would be a potential Gold Farmer or Buyer. This is a simple way of controlling the trade.

Except for the fact that I continually get accused of being one on the forums. First for mining where "I don't belong" and now for "arguing with this."

The general idea is that they have a negative impact on the economy by driving inflation. By maximizing income and minimizing loss to money sinks, they create more gold than they spend. The more gold in the game, the higher prices rise, generating inflation. This cycle is augmented by gold-buyers because they can afford better gear in less time. Better gear generally leads to quicker rewards, which further pushes the inflationary cycle. Taken to the extreme, it would be technically possible (if Turbine were completely asleep at the wheel) for prices to reach a point where only gold-buyers could afford anything.

As to the OP: The best way to eliminate Gold Farmers is to report them. Griefing legitimate players and/or eliminating legitimate gameplay elements is not an acceptable method. You could just as easily eliminate the problem by making everything Bind-on-acquire and removing all currency from the game. The question is, is it worth it?