Smoking's Real Health Effects
Circa 1937, the American Lung Association found that incidents of cancer were on the rise, and members therein were looking for any social phenomenon that could explain such a rise. At the time, smoking was the only real link, and as such a massive marketing campaign was initiated, lasting to this day, to 'reeducate' the public as to the 'health detriments' of smoking in terms of The Cancer.
Fast forward to a couple of years back, when a study appeared explaining that, at the same time as the above, incidents of tuberculosis were dropping. The reason found for this was that incidents of cancer were being misdiagnosed at the time as tuberculosis, but as diagnostic technologies were advancing cancer was increasingly being properly diagnosed. This led to the perceived rise of cancer in the general public.
Cigarette smoking affects the body in ways that your typical media organisations, churches to which most people have freely given their thought processes, would not prefer to have you know about. It toxifies the bloodstream, causing the immune system to work to flush the foreign invaders out of the system. At the same time, cancer is far, far less likely to be able to survive in such a toxic environment. And since we all know that the immune system is also what fights cancer, smoking is, in many cases, an effective way to help the immune system keep cancer at bay.
It also helps prevent against Parkinson's disease if you start between the ages of 25 and 45. But you already knew that.
There are only a few instances where smoking can be detrimental. The obvious is related to cases where an individual has preexisting conditions leading to pneumonia or other lung issues. In addition, if your blood vessel cell walls are naturally weak (which is likely due to low cholesterol intake), high blood pressure (which smoking and other activities can cause) may break the seal, so to speak, leading to strokes and what-not.
In effect, judging from the responses in this thread, smoking's only real health effect is allowing the individual to become lax in the act of conducting their own research to gauge the truth for theirself.
On a final note, labelling a smoker as an addict is unfair to the rest of the human race, members of whom are all addicted in one way or another to substance intake. A whole article could be written about how the body attempts to maintain a certain status quo of protein and nutrient balances, and as such implements an effect of 'addiction' to maintain those levels of substances. The side effect is the ability to become addicted to a wide range of other substances that have not-so-beneficial impacts on the body.
For the record, I have had no formal health training nor do I work in the field of health. All of this information is available to those who are willing to spend a few hours of time researching with an open mind.
(Nice religion you've got there. But mine's better. Want some?)