No cause they'd run into the diablo 3 auction house problem. That and if you think paid carries for raid weapons or trials gear is bad now, it'll be way worse with people charging hundreds for a raid exotic (which the owner can pull an infinite number of). In theory yeah trading is neat but it'd have to be heavily restricted for it to work such as: Can only trade for x minutes after activity completion and only with members of the fireteam so long as they didn't leave or join during the session (similar to flawless triumphs). Can only trade items that dropped during that session. Exotics of any kind are not allowed, full stop. Adepts of any kind are not allowed. Those are the restrictions I can think of that would either prevent entirely or make selling gear for real money very difficult.