My concern is not that e-cigs are dangerous (they might be, but they're very probably not more dangerous than actual tobacco), but that e-cigs' perceived safety might eventually get people, a lot of them, to start actually smoking.
Personal anecdote: I'm an ex-smoker. I love that e-cigs are helping smokers quit, but I don't like that e-cigs are getting non-smokers addicted to nicotine.
I'm not enthusiastic about banning things in general, and e-cigs are no different. But as someone who was dependent on nicotine for years, I hope The Public is wary: nicotine goes from being your lover to being your boss very very quickly. And once it's your boss, all it does is make you feel terrible if you aren't consuming nicotine.
If you have a nicotine habit: try to kick it. Life's great on the other side.
If you don't have a nicotine habit: life's great on the side you're already on.