Facebook's 800 million users have uploaded billions of digital photographs to the social network. Not only is Facebook is the single largest repository of photographs in the world, it has singlehandedly made facial recognition a viable business.

"We wouldn't exist without Facebook," said Gil Hirsch, CEO of Face.com, a preeminent provider of facial recognition technology on the Internet. "By far the biggest scale for face recognition is your friends on Facebook."

Facebook also has its own facial recognition technology, Photo Tag Suggest. It works the same way that Google's Find My Face does, with one glaring exception.

Photo Tag Suggest scans users' and their friends' photos for recognizable faces, and suggests nametags for the faces by matching them with users' profile photos and other tagged photos on the social network. But unlike Find My Face, Facebook automatically opts its users into the service.

Privacy advocates and regulators lashed out at the company for quietly turning on the feature in December 2010 without announcing it to users. The company apologized in June and developed a way for users to opt out of the suggestion feature.

By David Goldman @CNNMoneyTech - Last updated December 13 2011: 1:55 PM ET
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