Today, cigarette smoking remains the No. 1 cause of preventable death in the United States. So why are cities and towns coast to coast taking harm-reduction alternatives off the shelves while allowing Marlboros to remain? Last month, San Francisco banned the sale, including the online sale, of e-cigarettes. Around the same time, Brookline, a Boston suburb, did the same thing. Livermore, Calif., followed suit. Also moving in this direction are Morristown, N.J., Blufton, S.C., and Seattle.