Yes and no. I think there should be an option to trade, but I think it should be much more than an open trade. It should be tedious. Say, for instance, an exotic/legendary can only be traded for something or some set of relative components in return. Maybe (random idea) an exotic/legendary weapon could be traded for an exotic shards, etheric light, glimmer, strange coins, motes of light, etc. Also make each of the previous items have some set of things needed to trade in order to gain them through trade as well. As I said, make it tedious. I think that is the only true way to guarantee that some guy doesn't pay 20 bucks to some other guy and get a ton of exotics or something. Either that or make an Auction Vender that sets the price that cannot be bypassed.