EVE Online's developer, CCP Games, has approached the problem of the war on real money wow gold trading (RMT)f Aion a few different angles.
After all, if this practice of outright buying in-game assets with real world cash is going to happen in EVE, as with most MMOs (and regardless of what the developers try to do to curb this) it might as well be via a system the devs can regulate.
PLEX is an in-game item that represents game-play time and can be bought, sold, or traded on the open market in-game. PLEX has been integral in combating the numerous shady ISK selling websites in operation and CCP's dev blog last week showed how the player-base is starting to embrace this system.
CCP's operation "Unholy Rage" is a major offensive against the RMT operations exploiting the game, and is the subject of a dev blog f Aion EVE Online's GM Grimmi.
It's a slippery slope, and CCP's approach to the problem does have some critics, but thus far it's been successful. PLEX has only been one facet of their battle against the ISK spammers, sellers, and the virtual armies of macro-using operations, though.
Central to their strategy of combating sellers of the game's currency called ISK (Interstellar Kredits) is to offer another way for players to exchange real world currency for the virtual in EVE Online -- "PLEX", or the 30 Day Pilot License Extension.