Never happen and here's why. One person gets 6 gallys and lots get none. Well now instead of destroying said gallys he trades 5 of them and get something in return from 5 other people. As you can see in a very short time everyone would have a gally and icebreaker and probably every other exotic out there. So now the only way to make it so not everyone has all the weapons is to make them drop even less frequently than they already do, therefore everyone quits grinding VoG and other hotspots for exotics and instead just does exotic bounties in hopes that they can trade their reward off to one of the lucky players with multiples of same weapons. Then VoG doesn't get played anymore and eventually Crota's raid as well and everyone quits playing because the rest of the game suck and bungie goes broke and has to sell actual crack instead of its digital equal.