I think it's stupid to willingly do something that shortens your lifespan and raises your risk of disease, let alone to pay for the privilege. Cigarettes literally contain bleach, and you're paying a company so you can breathe it into your lungs. I think it's stupid, but I'm not about to try to stop you from doing it.
What I take offense to is when someone smokes a cigarette in such a way/place that I am forced to breathe their smoke too. IMO, the problem with cigarettes isn't that it's harmful to the smoker - their bed, let them lie in it - it's that it's harmful to everyone else around them. The smoker is forcing everyone else to smoke their cigarette too. If you want to mess up your lungs, more power to you. But don't expect me to let you mess up my lungs.
Now, nbamaniac, you've said that you're considerate and try to keep your smoke to yourself. I respect that. I still think it's stupid that you smoke, but it's your choice and you're doing what you can to keep it as a choice that's only yours. Unfortunately there are a lot of smokers out there who are seemingly of the opinion that they can smoke anywhere they want, and screw anyone else. Those are the assholes I have a problem with.