Last week, on a sweltering Monday afternoon, Luke Gerke was pacing in front of his East Village home in Manhattan, engaged in that all-too-familiar pastime: Waiting for a technician to install his internet service.

Only in this case, the rep who showed up wasn’t a uniformed service person from Spectrum or Verizon. It was a smiling neighbor who lives blocks away. Dressed in black jeans and a ball cap, Brian Hall arrived towing his installation gear on a handcart.

“Hey...