When they were pretty much common, but not yet the norm, I remember a very young woman weaving back and forth across the sidewalk. I had just assumed she was drunk, but nope, on the phone. When the bluetooth hands free stuff first came out it was very disconcerting because you couldn't tell if someone was on the phone or arguing with their imaginary enemies. Couple years back there was a Pokemon game fad so the parks and MUPs were filled with people wandering along staring at their phones expecting others to babysit them.