Beningnuman – “I have seen some rabbonim argue that Rav Moshe would agree that smoking is assur today because the chances of it causing a smoker’s death is over 50%”
I think this statement requires clarification. It is pretty unusual(if not unheard of) for someone to drop dead from smoking. What you probably mean is that it causes people to die at a younger age than they would have otherwise in 50% of cases. But I would think that that would put it in a very category than something dangerous that could cause you to die on the spot. There is a big difference between doing something that can cause you to lose your life on the spot and doing something that might lead to your getting sick and being nifter at the age of 70 or 80 instead of 90 (which is what I think happens to most people who smoke).