Luckily the public voice chat would basically have an "on/off" switch. They've already been talking about it at Bungie so you don't NEED to join a fireteam in order to have voice chat with others. Until that happens, I think matchmaking in the IB is pointless if you can't join fireteams with friends every time you personally want to run some IB. And God knows when they will actually add that option in, which is why I think it would be a little more incentive to stay in if we still got 5 rep for losing.