I recently had several instances of e-cigs/vaping at my ballet company. While an individual company can create their own policies, local bans are still in process. I was asked to help write up a company policy regarding e-cigs, after I walked into the break room of our studios and noticed a huge cloud of "smoke." I had to do a fair amount of searching to try to find any "back-up" material for our decision.
The main issue with the vaporizers is that they are flavored (strawberry, bubble gum, etc), brightly colored and indirectly marketed to children. A study was done in the SF Bay and it was found that 60% of vaporizer users in middle school had never smoked an actual cigarette. (And the total count of middle school users was 160k in SF.) And yes, they can contain capsules with hash oil in them, which is why so many parents are up-in-arms about them. Our ballet building also houses our school of over 350 students, so that our was company's reasoning for banning vaping in the building. We don't need for it to look cool to young impressionable minds, just because the professional dancers are doing it inside.
Shortly after our ban, we had a stager come in from Europe. I was shocked when I walked into the studio on a break and she was using her vaporizer. HR spoke with her about the ban for the company, and requested that she please vape outside. She did accommodate, at least when she was being watched.
There haven't been enough tests done on the long-term effects of these vaporizers, and while someone may have chosen to inhale that into their body, I don't want to have it in my body. I will say that the smoke/vapor from them does hang in the air, and you can walk through it and inhale it.
On Matthew's comment - I recently called Twyla Tharp's In the Upper Room - which is a 39 minute ballet performed in a giant block of haze. The entire stage is filled, and of course, the backstage, and when the curtain goes out - most of the audience. No, I was not a fan of sitting backstage inhaling all of this haze for more than 1 hour, but I was actually more upset when an Artistic Staff member came up to me between cues and blew his scented vaporizer smoke in my face. He said he was "helping with the atmosphere." He was doing it to be funny, but it upset me - as here was a leader of my company vaporizing inside the theater. Not the best role model.
I will say, it should come down to common courtesy. Granted, food isn't illegal, but many theatres post notices that say you can't bring food or drink into the theater. We also say that photos and videos are not permitted. We also ask people to silence their cellphones. If a theater says "no smoking" that should also include "no vaping, no e-cigs." For those blue tips that light up, it can be distracting to audience members as well as performers. And anyone who sees a cloud of smoke puff up - there are psychosomatic reactions (like coughing), or someone could yell "fire!" - because people don't know what it is.
It really should be a matter of common sense, but I feel that anyone who is smoking anything while inside a theater should be asked to stop.