You pose a very interesting question, which is at the heart of the matter. It's that the potential benefit would be maximized when the great majority of smokers substitute entirely for electronic cigarettes. If that happens, the potential will become important.
There's a problem we see, at least in the research that has been published in terms of clinical trials, which are very limited in terms of how efficacious they are.... This doesn't amount to a body of evidence, but some of them show that they have a low efficacy, which leads basically to dual use in most of the smokers. It's difficult to know whether that's good or bad, because obviously you can make the argument that, well, if you smoke two cigarettes less a day, that's an advantage. The problem is a sore one and it's difficult to respond to, but there are two other questions you have to pose.
One, we know that the maximum benefit from quitting smoking is not necessarily in reducing the amount of tobacco. The risk reduces primarily from the duration of the use and not the amount used, so that's a concern. I'm not saying that this is the only factor to consider, but the fact that people will continue using tobacco will mean that the potential benefit of electronic cigarettes is greatly diminished.
The other thing is this: what does it mean to have dual use? I think we can agree that the ultimate goal is obviously to switch entirely from tobacco to ENDS and, if possible, to abandon the addiction to nicotine. Whether dual use is able to achieve that in the long term or offer possibilities to go back to the use of tobacco is something that is uncertain.
I'm sorry that at this point I have more questions than answers, but it is indeed a very important issue.