The problem with real-world money entering a mmorpg enviroment is that it attracts petty crime and gambling addicts.
I recall when a player on Battlenet (DiabloII) successfully sold a virtual item on eBay - the whole game enviroment collapsed into a hackers magnet and scammers pitch. And minors played for hours and hours attempting to get that elusive rare item dropped - thus becoming addicted in the same way as gambler would to a fruit machine or a scratch-card game.
If game writers would write in a clause in their license that prohibits their virtual currency being exchanged for real-world value, this petty crime would never prevail so the game-play and social activity would be allowed to dominate.
ETA: as I was saying...
http://blogs.techrepublic.com.com/tech-news/?p=907 "Top RPG player kidnapped and tortured for password"