Tiefling, I respect you point of view, but all you cite is anecdotal evidence. While cigarette smoke is the leading cause of lung cancer, there is more than one way to develop the disease. I also agree that asking those around you first before smoking up would be polite, but the smoker and property owner has rights too, as explained in point two. Below are two paragraphs from the appendix of For Your Own Good by Jacob Sullum of Reason Magazine.

Secondhand smoke poses a grave threat to bystanders.

The evidence concerning the health effects of secondhand smoke is not nearly as conclusive as the evidence concerning the health effects of smoking. The research suggests that people who live with smokers for decades may face a slightly higher risk of lung cancer. According to one estimate, a nonsmoking woman who lives with a smoker faces an additional lung cancer risk of 6.5 in 10,000, which would raise her lifetime risk from about 0.34 percent to about 0.41 percent. Studies of secondhand smoke and heart disease, including the results from the Harvard Nurses Study published in 1997, report more-dramatic increases in disease rates—so dramatic, in fact, that they are biologically implausible, suggesting risks comparable to those faced by smokers, despite the much lower doses involved. In any case, there is no evidence that casual exposure to secondhand smoke has any impact on your life expectancy.

If secondhand smoke really is dangerous, smoking ought to be banned everywhere, except in private residences.

Since almost all of the epidemiological evidence about the health effects of secondhand smoke relates to long-term exposure in the home, the fact that this is the one place exempted from current and proposed smoking bans suggests a residual concern for property rights. Yet business owners have property rights, too. If the government respected their right to establish rules about smoking on their own property, potential employees and customers could take such policies into account when deciding where to work or which businesses to patronize. Whether secondhand smoke is a health hazard or merely a nuisance, such a voluntary system is the most appropriate way to deal with the conflicting demands of smokers and nonsmokers, since it allows for diversity and competition, rather than simply imposing the will of the majority on everyone.