The problem with vaping is the possibility that more and more people will do it, on the unproven basis that it's safe. More and more nonsmokers, anyway. People who may have never inhaled anything but air (although how clean is that these days, haha). For smokers, however, vaping is a fantastic alternative. Most ex smokers seem to feel considerably better after the switch, which says a lot.
With fruit loops cereal and jolly rancher flavors out there, however, it appeals to everyone. Whenever I vape, people around me want to try it, they smell the flavors and see the process of it all. For some reason people seem to like "smoke" in their lungs. And most all of us enjoy flavors. Fortunately, most of these people (in my experiences) decide to opt out of actively getting into vaping, because they realize it's an unknown risk. And I also actively persuade them not to unless they already smoke cigs.
There is no doubt that vaping has to potential to cause damage to our lungs/mouth/throats. Nicotine is an irritant and inflammatory agent, period. The science is in, people. I've experienced wheezing and mouth-sores after extending vaping. The convenience and cost also increases likelihood to chain vape, which may be considerably worse for our health (that's intuitive, no?). In addition, flavors are so diverse, that the potential for a toxic reaction to occur is not insignificant, as has seen with diacetyl. Statistically, it would make sense we will see similar cases in the future with different chemicals (Hell, it isn't good to even digest this stuff). In fact, all the different flavorings, temperatures, and coil materials are part of what make the health of vaping a complex topic. Maybe only overheated coils are damaging. Maybe only popcorn flavors are. Maybe TC nickel coils are. It all remains speculation at this point, and the tremendous amount of variables make the science more difficult.
If you can quit cigarettes by using an e-cig, do it. It's a godsend for many of us, and we should be free to vape. But please do not start vaping because you think it's safe or it has cool flavors. And please don't encourage friends and family to because it got you off cigs and you think it's safe.
Just my 2 cents.