I'm not a smoker, but I wonder: is there a downside to just continue using an e-cigarette? It's the smoke that kills you (and those around you) after all, not the nicotine.
There are, however, plenty of social reasons, depending on the local culture.
Not everybody necessarily realises that e-cigarettes are harmless to them and get upset when you use one around them, for example. Or people have had unpleasant experiences with aggressive e-cigarette consumers using them in public places like a restaurant or a train and getting uppity when asked to stop.
Another social stigma is that e-cigarette users tend to wax lyrical about them and, and I say that as an ex-user, not be very pleasant conversationalists, at least in the first few weeks after the discovery. I have seen people in social occasions actively avoid e-cigarette users (me!) for fear of being dragged into yet another lecture about vaping.
I'm quite delighted that some of my coworkers use e-cigarettes, since I can spend time around them without having to stand the horrific smell.
How can they make it more addictive?
Let's take the fact that manufacturers are making e-cigarettes addictive as a given. I'm not entirely sure how that works and suspect you're talking about the juice rather than the actual device, but the distinction is not terribly relevant in that conversation.
So, ok, let's assume e-cigarettes are becoming more addictive. How does that correlate to more harmful? there are plenty of things that are highly addictive and not bad for your health in themselves - sex, say, or running for some people, or programming.
Your point about addictivity is interesting, but I don't think it tells us anything about the dangers of e-cigarettes, real or imagined.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3538475/
> A routine of regular exercise is highly effective for prevention and treatment of many common chronic diseases and improves cardiovascular (CV) health and longevity. However, long-term excessive endurance exercise may induce pathologic structural remodeling of the heart and large arteries.
> Emerging data suggest that chronic training for and competing in extreme endurance events such as marathons, ultramarathons, ironman distance triathlons, and very long distance bicycle races, can cause transient acute volume overload of the atria and right ventricle, with transient reductions in right ventricular ejection fraction and elevations of cardiac biomarkers, all of which return to normal within 1 week. Over months to years of repetitive injury, this process, in some individuals, may lead to patchy myocardial fibrosis, particularly in the atria, interventricular septum, and right ventricle, creating a substrate for atrial and ventricular arrhythmias.
> Additionally, long-term excessive sustained exercise may be associated with coronary artery calcification, diastolic dysfunction, and large-artery wall stiffening. However, this concept is still hypothetical and there is some inconsistency in the reported findings. Furthermore, lifelong vigorous exercisers generally have low mortality rates and excellent functional capacity. Notwithstanding, the hypothesis that long-term excessive endurance exercise may induce adverse CV remodeling warrants further investigation to identify at-risk individuals and formulate physical fitness regimens for conferring optimal CV health and longevity.