Facial recognition technology was advancing faster than the legal and regulatory frameworks designed to govern it—and in 2012, a wave of startups and established tech companies were competing to build the most accurate commercial systems, with Google among the most closely watched participants.

The technology works by mapping the geometry of facial features—the distance between eyes, the shape of the jaw, the contour of the nose—and creating a numerical representation that can be matched against a database of stored images. Modern systems trained on millions of photographs can achieve accuracy rates that exceed human recognition under optimal conditions.

Google's entry into the space, primarily through its acquisition of face recognition startup PittPatt in 2011, raised questions the company itself seemed ambivalent about. CEO Eric Schmidt suggested publicly that facial recognition was "the one technology Google has decided to hold back" over privacy concerns—a rare acknowledgment from a company that typically moves aggressively into new technological territory.

The concern was specific and concrete: a mobile application capable of identifying strangers on the street by photographing them would fundamentally alter the possibility of anonymous public life. Stalkers, abusers, and authoritarian governments all have obvious use cases for technology that eliminates the anonymity that physical public space has historically provided.

Competing companies were less hesitant. Facebook had deployed its own facial recognition across hundreds of millions of user photographs. Law enforcement agencies had begun building large biometric databases.

The question of who would set the norms for this technology—companies, governments, or users—remained entirely unresolved. The faces, meanwhile, kept accumulating in databases.