I could be wrong here, because I've not tested it yet. But it seems like smokes are rendered client-side rather than server-side, meaning that the smoke plumes look different to each player looking at them. This essentially makes throwing smokes a gamble--can they see me? Will I see them? Will both of us be totally blind?
Again, maybe they are rendered server-side, but it seems like different players are experiencing wildly varying degrees of visibility in smoke.