Supporters of facial recognition technologies said they can be indispensable for catching criminals or finding missing people. But critics warned that they can enable mass surveillance or have unintended effects that we can’t yet fully fathom.

Lauren A. Rhue, an assistant professor of information systems and analytics at the Wake Forest School of Business, said the #10YearChallenge could conceivably provide a relatively clean data set for a company that wanted to work on age-progression technology.

But she added that Facebook already has billions of photographs on its platform, and people should be wary of any company being in possession of such a large trove of biometric data.

“The risk in giving up any type of biometric data to a company is that there’s not enough transparency, not only about how the data is currently being used, but also the future uses for it,” she said, pointing to another form of biometric data, DNA, which is increasingly being used by law enforcement to track down suspects — something many people might not have anticipated when they volunteered saliva in exchange for help tracing their ancestral roots.

“There are things we don’t think of as being threats,” Professor Rhue said. “And then five or 10 years from now, we realize that there is a threat, but the data has already been given.”

Like the rest of us, Facebook looked different 10 years ago. In 2009, the “Like” button was introduced, and the site unveiled a new home page to make it easier for people to see their friends’ posts in real time. Facebook also reached 360 million active users in 2009; now, it has more than 2 billion.

Facebook announced that it was using facial recognition technology in 2010. When people upload photos of their friends, Facebook can use the technology to suggest the names of people in the picture. It can also alert users if they are in a photo posted by a friend.