I think the key to making this system work is to simply make the economy a smaller part of the game. Focus on a skill based action game with very few collectible resources that make a decent (useful) variety of weapons and gear. This gear wears out over time and needs repaired or replaced, thus enters a nice shallow engaging, player created and player driven economy. If the players want to expand that economy, they will always find a way (diablo 2 and ebay is a good example of this) thus a developer can focus on DLC expansions on these community driven designs.
Here is another suggestion, create in game systems to allow players to decide on how to handle theft and fraud. Allow players to earn the authority to, for example exile a player from a city (city guards upkeep this authority) or force them to fight in an arena (bigger draw backs to arena death) or even get right into the gears of the game and strip players of hard earned skills and items. Bounties, coops, elections, drafts, etc. Plenty of systems of power earning, enforcing and power distribution exist, giving players the chance to incite change within a game is what really makes an economy fun. Economy is the distribution of power not things that drives peoples. Enabling players to empower themselves based on the opinions of other players, I think, is the key to this system. I mean how incredible would it be if players of an MMO discovered a better way to govern and socially organize?
Democrats, republican and the WOWicans, it would only be a matter of time if we give players the tools to play at socially organizing.