The more I think about this, the more I have to respectfully disagree. I'm not meaning to belittle you or anything, but the research I've done on this says differently. So, I just want to put both viewpoints out there and let people decide for themselves.
The research I have read indicates that nicotine produces a chemical so similar to dopamine (a chemical that the brain naturally produces that keeps us from being depressed) that when we first start smoking, we are bombarding the dopamine centers in the brain. So, as a defense, the brain stops making dopamine on its own. That's why when we first start smoking, we are lightheaded. But after smoking for a while, we don't get that "lightheaded" sensation anymore. And when we continue to smoke, we are getting SO much dopamine in our brains that our brain's second line of defense is to shut off some of the dopamine centers in the brain, so that essentially, our brains completely stop producing dopamine and have fewer receptive centers for it because we're getting so much dopamine from smoking.
So when we quit smoking, most people experience depression. Well duh! Dopamine is a chemical that keeps us from getting depressed. Wellbutrin and Zyban help the brain start making dopamine on its own again and over time, the dopamine receptive centers open back up again and the brain starts making dopamine normally again, and the depression goes away. For more on this, you can read Shevie's Rewards, Nicotine and the Brain in the General Forum. I'll bump it.
My fear is that if newer quitters think that from birth, they are missing a chemical in the brain, then they will NEVER be normal again without smoking. That's not true. Our brains WILL start producing dopamine again on their own, but it takes time.
As for the daredevils, they aren't missing anything either... they just enjoy the "adrenaline high" or "adrenaline rush" that they get when they do those stunts. In a way, I guess they are addicted to adrenaline, but any one of us would get the same high if we were to do those stunts as well... but for most of us, our fear is greater than the desire for adrenaline. Does that make sense?
Mercy, I'm not trying to undermine you here... again, I just don't want newer quitters to think that they are