I recently have my first (and only, so far) issue with vaping in public. There is a local bar and grill I have been patronizing for several years. Every other Tuesday a bunch of co-workers and I often go after work (it is our payday). Everyone in our group knows about my PV (a Darwin, in this instance) and is fine with it. My city recently went to a 'no smoking indoors' policy. A lady seated 30 feet away, and saw me exhaling. She came to my table and got in my face about it.
Lady: SIR, THIS IS A NO SMOKING TOWN, PUT THAT OUT NOW!
Me: I am not smoking. This is an electronic cig, no tobacco, no smoke, no fire, no ash.
Lady: YOU HAVE BEEN TOLD ONCE ALREADY TO PUT THAT OUT! NOW DO IT!
Me: No, I have been using this for three months in this establishment. I have asked permission to use it.
Lady: (apparently ran out of something to say, went back and sat down).
The icing on the cake, was shortly after that our waitress said "Hey, can I have a hit off of that?"
I could have said a lot more, but I remained polite, and did not want to make a scene at a place where I am a semi-regular. I didn't want her to make more of a scene than she did, or to complain to anyone. If someone complains to the owner, whether it is valid or not, the owner doesn't want unhappy customers.
I later realized I could have probably avoided it, by changing a habit I still have from when I was a smoker. Whenever I was around non-smokers, I always had the habit of exhaling straight up. This made me more visible from 30 feet away. Since vapor basically falls anyway, I should exhale down while in public.