What's the etiquette with electronic cigarettes?

An e-cigarette led to confusion on the M6. But what are the rules of smoking fake fags? A misunderstanding over an electronic cigarette caused a major terrorist alert on the M6 yesterday. The incident showed what a novelty e-cigarettes are to many people and how easily confusion can develop. But the "fake cigarette" also raises questions of etiquette.

Even before the smoking ban, a restaurant-goer lighting up would annoy fellow diners. Since the ban, such behaviour would cause consternation among customers and lead the owner to fear legal action. Smoking an e-cigarette, however, is legal in public places. Although it contains nicotine, there is no burning and only odourless steam is produced. The health advantages of e-cigarettes over tobacco smoking have attracted celebrities including Leonardo di Caprio and Kate Moss.