I actually had my first (semi) run-in with this issue earlier tonight while I was out to dinner with a good buddy of mine and his folks. We were at a "donation based dinner party" out in the county where his folks live. Real cool place, fantastic wood fired oven, killer pizza. My buddy and I are both cooks by trade and education, so we had spent most of the dinner hanging out and chatting with the woman running the event and her husband, who has actually been trying to quit with ecigs and asked me about mine when he saw me semi-stealth vaping (not so much stealth vaping as just not drawing much attention to it) as he had never seen one like mine.
We (my buddy, his folks, and I) were heading out with another couple, who had a very young daughter I had been, and continued to be, careful to avoid vaping around out of respect for them. His folks had seen me vaping earlier, asked me about it, and once I explained it to them commended me on my recent week without cigarettes. I was getting a few puffs in before we got in their car to head back to their home, and the woman from the other couple comes up behind us and asks "Are you smoking?". I answer no, and explain what an ecig is, what is in the juice, what is in the vapor, and that it allows me to get the nicotine I enjoy in a greatly harm reduced manner, using the typical caffeine comparison. She gives me a sort of scoffing look and says something to the tune of "Or you could just not use anything." Irk'd the $#!% out of me, but I refrained from saying anything else because she is friends with my buddy and his family, and anything I would have said would have probably resulted in me reacting in a typical "kitchen" manner (I have a very direct, no BS taken manner of dealing with folk)... which just isn't something I honestly like to deal with all that often.
I just do not understand why people cannot let something that damn near boarders on harmless, and has NO IMPACT ON THEM WHATSOEVER, choose to criticize one small lifestyle choice I make. I enjoy nicotine. I plan on continuing to use it for the rest of my life, albeit in as healthy a manner as possible. That does not effect you. My vapor does not effect you. Leave it be!