I was recently at a dinner party at a friend’s house. In the middle of the meal, a young woman pulled out an electronic cigarette, took two puffs, then put it away. A few guests clearly wondered about the white smoke she exhaled. Shouldn’t people excuse themselves to indulge their addictions in private? This bothered me because she was among friends and shouldn’t have needed the security mechanism of a cigarette. What do you make of this?

D.G., East Hampton, N.Y.

Electronic cigarettes, for the uninitiated (or anyone who hasn’t seen a paparazzi shot of Jack Nicholson or Leonardo DiCaprio lately), are battery-powered vaporizers, often in the shape of cigarettes, that deliver synthetic nicotine (the addictive agent in old-time ciggies), without many of the harmful substances, which is not the same as calling them safe. Users exhale an odorless white vapor. (Are you with me so far?)

These e-versions are said to be cleaner and safer than tobacco products. But I couldn’t find any definitive study about their safety, addictive qualities or hipster cred for users or those of us who take in secondhand vapor. And the laws regulating them are all over the place. This is terra (relatively) nova.

Now, on to your dinner party: The “vaper” (yes, that’s the colloquial term for users) should have asked your host and tablemates if they minded her electronic puffing. E-cigarettes may be newish, but courtesy is not. And blowing anything in an enclosed space, even wispy plumes of vapor, calls for consent — and inevitably, a show-and-tell. Several users told me that the dreary seminars they are forced to lead every time they whip one out have driven them to the privacy of restrooms anyway.