Texting while driving is not a good idea, and is illegal in a lot of places. But texting while walking? That's just annoying, with people wandering about slowly instead of keeping up a decent pace. In China, where the sidewalks can get really crowded, they have a solution: special cellphone walking lanes like this one in Chongqing.
According to Yahoo Tech, this was tried in Washington earlier this year as a promotional stunt by National Geographic, but that it didn't work very well; "Many people actually using their phones did not notice the markings at all. Of course they wouldn’t: They were staring, oblivious and glassy-eyed, at the screens of their mobile devices."
But seriously, walking is a major form of public transport that needs more space and more consideration. Perhaps there should be fast lanes and rules of the road.