A beta update for Steam lets gamers trade virtual items for unused digital copies of games. Released Tuesday, the upgrade to Valve’s digital-distribution platform could co-opt a thriving black market in which players swap unwanted games for prized in-game extras.

Valve introduced hats — novelty pieces of headwear for game characters — to its cartoon-styled multiplayer first-person shooter Team Fortress 2 in 2009. These hats, along with upgraded weapons, could be earned by simply playing the game or by purchasing them with real money. In 2010, Team Fortress 2 received an update that allowed players to trade hats and weapons with each other.

Now you can trade those hats and other virtual goods for other players’ unused games.

“Any game you’ve purchased from the store as a gift, or received as an Extra Copy, can be traded to other users,” explains the Steam trading FAQ. “They can be used to trade for other gifts, or for items in Team Fortress 2. We’ve added a new checkout option to the Store when purchasing a gift so you can save it for trading or sending later, to support users who want to save games for trade fodder.”

What this means is you can’t trade away an old, unplayed copy of something like Railworks 2 for a shiny new Teddy Roosebelt. Instead you have to buy the game again, this time as a giftable version.

Exchanging a virtual gun or hat for a fully playable game isn’t a new idea. Users of Steam, Valve’s digital-distribution platform that is home to hundreds of downloadable games including Team Fortress 2, have been doing it ever since the trading system was introduced a year ago. Until now, the practice was never official.

‘This is evil genius.’

“This is evil genius,” said Dubious Quality analyst Bill Harris in an e-mail to Wired.com. “Valve is co-opting a secondary market purely for their own gain because they’ve cleverly turned games purchased from Steam into currency and their cut of each transaction is substantial.”

Wired.com reached out to Valve for comment but didn’t get a response by press time.

We saw something like this recently with the news that Blizzard Entertainment’s upcoming dungeon-crawler RPG Diablo III will allow players to sell in-game loot for real cash. Like Blizzard, Valve is trying to control an economy that has until recently been entirely under the control of fan-run websites and forums.

But buying mystical swords and armor with real money is much different than exchanging a purchased game for a digital hat that you will rarely ever see. The sword can help you complete the game faster but the hat is entirely cosmetic — there’s little practical value.

On the other hand, goods are only as valuable as what you pay for them. If you pay $35 for that Legendary Sword of +1 Badassitude, then that sword is worth $35.

If I pay $50 for a game and then trade it for a new hat, is the hat worth $50?

If this experiment succeeds, then the answer will be yes. And Valve will have created an unprecedented virtual economy where a copy of Portal 2 is just as valuable as a Respectless Rubber Glove.