Now an industry consultant, Dr. Atick finds himself in a delicate position. While promoting and profiting from an industry that he helped foster, he also feels compelled to caution against its unfettered proliferation. He isn’t so much concerned about government agencies that use face recognition openly for specific purposes — for example, the many state motor vehicle departments that scan drivers’ faces as a way to prevent license duplications and fraud. Rather, what troubles him is the potential exploitation of face recognition to identify ordinary and unwitting citizens as they go about their lives in public. Online, we are all tracked. But to Dr. Atick, the street remains a haven, and he frets that he may have abetted a technology that could upend the social order.

Face-matching today could enable mass surveillance, “basically robbing everyone of their anonymity,” he says, and inhibit people’s normal behavior outside their homes. Pointing to the intelligence documents made public by Edward J. Snowden, he adds that once companies amass consumers’ facial data, government agencies might obtain access to it, too.

To many in the biometrics industry, Dr. Atick’s warning seems Cassandra-like. Face recognition to them is no different from a car, a neutral technology whose advantages far outweigh the risks. The conveniences of biometrics seem self-evident: Your unique code automatically accompanies you everywhere. They envision a world where, instead of having to rely on losable ID cards or on a jumble of easily forgettable — not to mention hackable — passwords, you could unlock your smartphone or gain entry to banks, apartment complexes, parking garages and health clubs just by showing your face.

Dr. Atick sees convenience in these kinds of uses as well. But he provides a cautionary counterexample to make his case. Just a few months back, he heard about NameTag, an app that, according to its news release, was available in an early form to people trying out Google Glass. Users had only to glance at a stranger and NameTag would instantly return a match complete with that stranger’s name, occupation and public Facebook profile information. “We are basically allowing our fellow citizens to surveil us,” Dr. Atick told me on the trade-show floor.

(His sentiments were shared by Senator Al Franken, Democrat of Minnesota and chairman of the Senate subcommittee on privacy, technology and the law. Concerned that NameTag might facilitate stalking, Mr. Franken requested that its public introduction be delayed; in late April, the app’s developer said he would comply with the request. Google has said that it will not approve facial recognition apps on Google Glass.)