Good to see everyone got their banners working

(I'd get one but I don't remember exactly when I quit)
Like others said, a snazzy one-liner to strangers sounds way too much like a sales pitch. I don't mention it to anyone unless they ask me or I know they are really trying to quit. As probably most smokers/ex-smokers know it is incredibly annoying when a stranger would tell you about the dangers of smoking, especially in a pompous way, like "really? You don't say? I didn't know!!" Informing people is fine, but just by vaping in front of them you are informing them enough as to where if they cared they should ask about it.
Almost the only people that care (in a good way) that I vape are non-smokers, and almost no smoker I know gives a crap at all, and thinks it's silly. I was hanging out with one of my friends who has been trying to quit since forever, and he was on nic gum, really hurting and twitching, etc, while STILL smoking (just less). I sat there happy as can be vaping away and told him about it because my non-smoking friend told him about the benefits, and I told him about the 510 I got for $35 online, instead of like 100-something they charge in the mall and that it is better and he actually told me "ppsssss! I wouldn't pay $20 for that thing!"... while shaking, upset, and spending whatever amount the nic gum costs, and STILL smoking at $8 a pack.... And I've had other experiences like that with smokers... They are adults, they can be stupid if they want to, I'm not gunna lecture anyone, especially if I don't know them.
And, again, I think a sales pitch would turn people off of vaping more than help them. I used to smoke a lot more when people gave me crap about it out of spite.
But that's my opinion. Good luck with whatever you decide. Cheers!