Valve started with a b lwa taprogramma on Steam that allows gamers to games and in-game items from Team Fortress 2 with each other can exchange. Condition for exchange is that the games and items have not been used.
For the time being, only in-game items in Team Fortress 2 tradable; Valve is planning to also Portal 2-items untradeable to make. Furthermore, Valve is interested gamedevelopers the ability to ruiloptie in their games to build. Gamers can sign up for the beta program in the settings screen of Steam.