There's no doubt that a good deal of us on ECF (maybe the 95% stated early in the thread) are dependent on nicotine. And, to be precise about that, we struggle to go any length of time without it before we suffer from a variety of withdrawal symptoms. In other words, we feel that we 'need' nicotine to function properly.
What's harder to know for sure is whether it was nicotine that got us here in the first place. Or, again to be precise, whether it was nicotine alone, since all of us became dependent on tobacco (mainly smoked) which is a plant with a variety of physiologically active compounds.
I like to think about nicotine in terms of the addictive process. Clearly it's addictive, because we're dependent on it, but is it particularly addicting?
Animal studies have shown that nicotine-naive rats don't find pure nicotine (injected) particularly "reinforcing" - that is to say, they won't go back for more. This is in stark contrast to whole tobacco which is very reinforcing.
What's the "mechanism" behind this "reinforcement"? Well, to put it simply, I'd say it's pleasure. Nicotine alone isn't particularly pleasurable, so rats don't bother with it. Tobacco, however, is. So they do. Is this indicative of addiction? No, but it does suggest that over time mammals are more likely to repeatedly use tobacco than pure nicotine, and so heading down the path towards nicotine dependence.
Of course, it's possible that e-cigs are pleasurable in and of themselves, despite lacking the other chemical compounds in tobacco, or it's possible there's some interaction between those compounds and nicotine which accelerate the addictive process. Fact is, no-one can say for sure right now, so we don't really know what the addictive potential of e-cigs is to nicotine-naive people.
There are other reasons to believe that e-cigs are likely to be less addicting than tobacco smoking: smoking is about the most efficient way (short of injecting) to deliver tobacco compounds to the body. It's somewhat canonical in addiction research that addictive processes are strongly related to the speed of delivery of a drug. E-Cigs, although they deliver nicotine faster than NRT also deliver it less acutely than smoking, and it is absorbed substantially slower. We should conclude, therefore that the likelihood is that e-cigs are less addicting than tobacco smoking on account of their lacking both efficiency of nicotine delivery and tobacco alkaloids. But how much less addicting, no-one can say.
Caveat: Addiction is a social construct with no single accepted definition. It's very important to include the psychological, biological and social aspects when thinking about any drug or substance.
Interesting links:
Karl Fagerstrom on rethinking nicotine addiction
ECF mega thread:
http://www.e-cigarette-forum.com/forum/nicotine/44958-so-we-getting-we-not-nicotine.html
Things not touched on in this post: The 'craving' (wanting) aspect of nicotine dependence, individual differences in addictive potential, age at which first exposed to nicotine << all very important.
Interesting things to think about: the sensory-motor aspect of e-cigs (tactile, visual, throat hit) and how they relate to smoked cigarettes. I.e. whether these important to us because they are replications of associations that are specific to us as previous smokers, or whether they pleasurable in and of themselves are are likely to be as pleasurable to never-smokers.
Also, the sensory nature of nicotine in e-cigs (throat hit), in addition to its pharmacological action.
