If I were Mayor of New York City I'd order all manholes be left uncovered, purely to weed out people who heedlessly walk the streets while staring into their cell phones. Mobile Facebook updates would be suddenly interrupted by sharp introductions to gravity, with only a doppler-effected scream to mark the event.
Perhaps the problem will increase now that at least one manufacturer will be providing users twice as much to stare at, and maybe cause copycats to follow suit: Yesterday Kyocera officially announced their upcoming Echo phone with two screens.
"Being able to compose an email while having Google Maps open or even having two browser windows open at the same time can literally change the way you work," wrote Boy Genius Report in their review. "...It changes the way we think about a smartphone in a lot of areas.... We can totally see it changing the direction of a mobile device's utility." Presumably the change in direction they envision is not a vertical drop, but I can still dream.