This was a good article about E-Cigarettes. I wouldn't be surprised if, years from now, e-cigs are determined to be very hazardous to everyone's health including people exposed to the second hand vapor. Its kind of disturbing. People can go to the bathroom, vape and leave no residual smell in the bathroom.. then someone else can walk in and get exposed to all their second hand poisons and not realize it at all.
http://gizmodo.com/why-e-cigarettes-might-not-be-as-safe-as-you-think-1589485508