That's a really good question and the one everybody wants to know the answer to.
We know it is impossible to clinically demonstrate nicotine dependence in never-smokers (it has never been possible to show the slightest sign of dependence no matter how much nicotine is administered or for how long), but ecigs have not been tested. Specifically, modern high-efficiency electronic vaporizers have not been clinically trialled for dependence potential with never-smokers.
It is quite possible that some dependence might be able to be created at a sub- clinically significant level: maybe 1 or 2 in 1,000 - perhaps even 8 in 1,000 - or something like that. The reason I say this is that there are two possible routes:
1. Some people can become dependent on anything with an active component, even when we consider such things as impossible to describe as 'addictive'. For example there are apparently a couple of cases on record of someone becoming dependent on carrot juice.
Obviously we would not consider this material to have any potential for dependence - as it doesn't. However there are infrequent cases of persons with a need for dependence - apparently - and they can, it seems, become dependent on virtually anything that causes a physiological change that the body/mind recognises. Perhaps it is a question of what they come across first that fits their need. It's explained by some model in psychology I forget the name of.
So by this definition, we will see rare cases of dependence. In practice it seems likely that ecigs will create about as much dependence as carrot juice, perhaps even a little more, since nicotine does have more pharmacological effect. If so, it will be unusual, of no clinical significance, and of no real importance.
2. There is also an issue of pyrolytic aldehyde generation and subsequent nicotine potentiation.
Nicotine dependence is believed to be caused by potentiation in tobacco vehicle delivery. Synergy and boosting may also be factors, we just don't know at this point [1]. The 'standard model' is that harman and norharman, which are aldehydes in tobacco known as MAOIs, and assisted by more aldehydes in tobacco smoke created by pyrolytic action, act together with nicotine to chemically re-wire the brain in a way that creates common and persistent (but not permanent) dependence on nicotine.
Now we are gradually becoming aware that super-heating e-liquid has the potential to create aldehydes in the resulting vapour. These compounds, which are either missing or at trace level in low-temperature vaping, may act exactly the same as the tobacco smoke aldehydes (as they are essentially the same). If this is the case, high-temperature vaping may have some potential for creating dependence on nicotine.
This concept occurred to me about mid-2014, and I've mentioned it occasionally since. Nobody else has suggested it so you could dismiss it as unrealistic. In my mind it is just a possibility, but it is there.
Looking at the practical aspects of this:
a) If a million never-smokers take up vaping, and some of them move on to sub-ohming, then maybe we will see a proportionate number who become dependent on vaping and/or nicotine because of this effect.
Currently it does not look as if the numbers involved will be substantial, because it entirely depends on large numbers of never-smokers starting to vape, and that they sub-ohm in significant numbers, and that this effect is not just non-zero but relatively strong.
b) It's also interesting to try and work out what the effect might be on ex-smokers who are already dependent on nicotine. Perhaps it might just make nicotine reduction or elimination more difficult.
Who knows
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[1] We could refer to chemical management of the delivery efficiency of nicotine in cigarettes, such as ammonia additions, as 'boosting'. Some call this freebasing.
Similarly, there may be some synergy (multiplication) due to co-administration with other WTAs such as anatabine, for which some evidence has been reported.
This area of nicotine research is weak.
