The PlayNoEvil blog has obtained gold sales information from one of the multi-game gold farming services. The service provided the site with currency sales values over a period of nine months. Site author Steven Davis examined the data with an eye towards the effectiveness of banning, anti-RMT task forces, design changes, and other preventative measures. If currency values went up, then there was obviously less currency entering the marketplace; this would indicate successful campaigns against the farmers. The result is a fascinating scorecard in the war on RMT. He's got data for Final Fantasy XI, Guild Wars, EVE Online, Runescape, EverQuest 2, and World of Warcraft.
So what does the data show? Essentially, that not a single thing done by any of the developers/publishers has had the effect of increasing currency prices. Moral outrage and crackdowns aside, prices for every currency tracked by the site have remained more or less steady. The only effort that seemed to have any effect at all was Jagex's recent trading technique patch, which temporarily spiked Runescape gold to twice its previous value. Since then, prices have returned to normal, indicating the farmers found a way around Jagex's changes. Though it's been noted elsewhere, it's also interesting to reiterate that gold prices on EverQuest 2's publisher-supported RMT servers don't vary from the norm across the game's servers. That is, even with a legitimate option people are still willing to engage in risky third-party RMT.
We want to make the observation that the RMT company involved here has every reason to falsify data. It's fascinating stuff, but should be taken with a grain of salt.