A Facial-Recognition Tour of New York

Kashmir Hill, the author of the new book "Your Face Belongs to Us," took a walk around midtown the other day, to check out a few businesses that routinely capture visitors' biometric data. She wore a red coat and white boots, and her hair was a faded purple. "Let's see if Macy's is still collecting face-recognition data," she said. Businesses that do so are required by city law to post signs alerting visitors. She'd noticed, earlier, that the store's signs were "very affixed to their walls."