As so often happens in technology, this invention went from curiosity to phenomenon before the laws could catch up. According to the Tobacco Vapor Electronic Cigarette Association, e-cigarettes have grabbed as many as 10 to 14% of the 44 million tobacco users in the U.S. And sales are on track to reach $1.7 billion by the end of the year. Despite the success—or perhaps because of it—the Food and Drug Administration has been eyeing the product with suspicion. But even though it threatens to ban online sales, the FDA still hasn't actually regulated the devices. 

Researchers haven't managed to clarify things either. For every German and French study that says e-cigs are harmful, there's a researcher from Boston or Philadelphia who says they offer very little risk to health or should be actively pursued for harm reduction from cigarettes.

Beware:  Varying Polices Ahead

There's only one rule to know about vaping in public, especially during this peak travel period: There is no one universal rule. Policies differ by industry, and sometimes within the same one.

Most airlines do not permit the use of e-cigarettes on board, but they do allow users to pack their batteries and juices in carry-on baggage. (Bear in mind that TSA regulations on liquids apply.) Most major American airlines—including United, JetBlue, American Airlines, Delta and Southwest Airlines—ban the actual act of vaping in flight, as do many international airlines like British Airways and Japan Airlines. Although it may be tempting to "sneak a vape," take this as a warning: You don't want to be the person who gets caught and makes an entire plane turn around. 

It's not just airlines either. Amtrak also forbids e-cigarette use. In general, transportation services are strict about anything related to smoking.

Hotels may be another matter, considering some still have smoking and non-smoking rooms. But every operation is different. For example, I've stayed at many bed and breakfasts, hotels and motels that met my vaping behavior with keen interest, not loathing. However, it's worth noting that none of them were a Marriott. The hotel chain charged one Chesapeake, Virginia woman $250 for vaping, citing the hotel's anti-smoking policy. 

The rules are even harder to pin down for restaurants, bars and cafes. Even though nicotine and caffeine are an infamous match, Starbucks doesn't permit e-cig use. Restaurants can be equally testy about the activity, as well as some bars. But not all of them. Nightclubs, like EMM Group's FL and Finale, welcome e-cigs. EMM Group co-owner Mark Birnbaum explained to The New York Times that they help discourage customers from leaving. “It’s hard enough for us to get them in,” he said. “Then you’re forcing them out on the street to smoke.” 

See also: http://www.businessinsider.com/e-cigarettes-passes-1-billion-sales-2013-8

I'd love to see them try to fine a child (or an adult that matter) for vaping.