Alex had a gnawing, uneasy feeling when he boarded the last BART train from San Francisco International Airport, on the way home from a business trip in 2012. The station was dead empty. The 33-year-old risk-management consultant was alone, shuttling to a quiet East Bay suburb after midnight, dressed like the straight man in a noir movie. Alex wore a suit with slippery pockets. He slipped his iPhone4 into one of them, took a seat on the Pittsburg-Bay Point train, and crossed one... More >>>