Ben Wolfson glanced up from his phone while walking in downtown San Francisco last week to see a woman whizzing toward him on what looked like a child’s kick scooter.
Only this one had an electric motor. “She was just barreling down” on the sidewalk, he said. Mr. Wolfson, 28 years old, jumped out of the way and shot her a “dirty look,” but said she didn’t react.
“She...