Even when smoking is conclusively proved to cause cancer and grotesque pictures of what your lungs will look like are displayed on the pack, people still ignore it and just smoke anyway. I think this effect is partly why people ignore or try and dismiss any possible evidence that this technology could indeed be causing harm. The NTP study has taken a lot of flak in the name of 'discerning' science,but as far as I can see none of it is deserved. (Original authors have responded thoroughly - so much so that they have done video presentation- on youtube)