Except the amount of nicotine indoors is far less than cigarettes. I'd imagine outside is almost nil.

> The emissions discharge water, volatile organic compounds (VOCs) and nicotine into indoor air at levels far lower than found with tobacco cigarettes (Schripp et al., 2013).

http://www.treatobacco.net/en/page_528.php

In addition, e-cigarettes dont always have nicotine and often have lower amounts than cigarettes. Further making the fear of momentarily sitting near someone smoking an e-cigarette outside almost irrational in terms of health risks.

In terms of not wanting vapor being blown in your face, then I agree there is a social etiquette that should be respected.