Is there such a thing? How do they do it?
While most people who start out as social smokers eventually become addicted, there are a few people who actually can have a cigarette now and then, and then put them down for long periods of time. Some recent biomedical information given at a speech by Dr. Rachel Tyndale of the University of Toronto, entitled "Genetic Variation in Drug Metabolism: The Making and Unmaking of a Smoker" suggests that it is due to the function of an enzyme, CYP2A6, which controls how slow or fast nicotine is metabolized in our bloodstream.
There has been research done by Dr Tyndale and her colleagues, Sellers and Kaplan, which has examined this difference in metabolic rate of the breakdown of nicotine. I had a hard time completely understanding just the abstract, or simple explanation, of their study, but it seems to suggest that this enzyme is behind the frequent or infrequent need for more.
I think it would be safe to say that those of us who become addicted are "fast metabolizers", where those who can remain "social smokers" are "slow metabolizers". Once they've had that hit of nicotine, they don't need more because it's still working in their bloodstream for a longer period of time. We nicotine addicts, however, metabolize the nicotine quickly, and thus we want more (crave it) very soon after.
Anyone else want to do more research on this, be my guest. I just thought I'd point you in the right direction.