I smoked for 30 years. I started when I was only 13 years old. I tried everything to quit, but was never able to actually do it. Gum, patches, Chantix, even acupuncture. The only thing that worked for me was e-cigarettes. I am sucking on one while I am typing this. No, they aren't safe (the user is putting a foreign substance into their body), but they are significantly safer than inhaling smoke from burning organic & synthetic materials. I feel worlds better and my lung function is better. My doctor is happy that I have given up smoking. FWIW, nicotine is no more dangerous than caffeine. The dangerous part of cigarettes is the thousands of toxins that are in the smoke. If you think of the nicotine as a medication (nicotine patches, gum, etc.), then I can confirm that e-cigarettes are probably one of the most effective delivery methods for someone who is trying to quit. Asthmatics use this delivery path regularly for their medications - which help them breathe. Yes, they put a foreign substance into their lungs to help them breathe.
With all of this being said, and the fact that I am a proponent of e-cigarettes, I am only a proponent to the point that it is a useful tool to help smokers quit cigarettes. If you don't smoke, don't start smoking or vaping. Finally, I always question the people who speak badly of e-cigarettes & ask them why they want to take a tool away from someone who could use it to quit smoking. It almost seems like they want people to keep smoking.
BTW, yes, I vape while riding my bikes.