Not between players no I don't think they should. But maybe a trade system between players and the vendors could work. Example, maybe you've got yet another of the exoti you always get. You don't want it, so you go to a vendor (let's say Xur) to trade it for another exotic. But here's the catch, obviously Xur only comes at weekends. Not only that but he only has a small selection of exotics for trade each week so you might have to keep hold of what you have for another week. And the final catch, its not just a straight swap. You swap your exotic plus you have to do a small "quest" type thing as well. This could be that you just have to pay like 50 strange coins as well, or even swap 2 exotics for 1. Or maybe even a small bounty or patrol type mission (like the relic harvests). That way there's no risk of players abusing a trading system, and there's also still a little bit of work to do to be gain the privillage of trading something. That's just an idea anyway.