As she made the long journey from New York to South Africa, to visit family during the holidays in 2013, Justine Sacco, 30 years old and the senior director of corporate communications at IAC, began tweeting acerbic little jokes about the indignities of travel. There was one about a fellow passenger on the flight from John F. Kennedy International Airport: “ ‘Weird German Dude: You’re in First Class. It’s 2014. Get some deodorant.’ — Inner monologue as I inhale BO. Thank God for pharmaceuticals.” Then, during her layover at Heathrow: