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Carl Mazur, a photographer in Utah, freaked out when he saw an ad for Rokinon camera lenses pop up on Facebook. That's because it appeared 20 minutes after Mazur's chiropractor mentioned the brand to him during a visit.

Mazur had heard stories about the social network eavesdropping on conversations through the mics on smartphones in order to deliver more precisely targeted ads. But he didn't give them a second thought. The ad for the photography gear, however, made him reconsider.

"That's when I was a true believer," Mazur said, adding that he had never searched or shopped for Rokinon lenses before. "I was like, 'This is weird.'"

Facebook has denied it listens to our conversations to serve ads. CEO Mark Zuckerberg even told Congress the company doesn't engage in the practice. Experts and analysts say Facebook doesn't need our conversations to target ads effectively. Nonetheless, the conspiracy theory -- now more than four years old -- persists, with people sharing their experiences in YouTube videos, Medium posts and social media comments.

Even if Facebook doesn't eavesdrop, the pervasive belief that it listens to us adds to its reputation for poor privacy practices. The perception is so pronounced that Zuckerberg referenced it at Facebook's developers conference last month, saying his company didn't have "the strongest reputation on privacy, to put it lightly."

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The reputation problem won't hit Facebook's growth anytime soon. It's still the world's largest social network with 2.38 billion people logging in every month. But little by little, analysts say, rumors like the eavesdropping conspiracy could change the way we use the social network. If we're worried Facebook is listening to our conversations, we might stop sharing some of our personal data, the information it uses to target ads so precisely. That would make it less valuable to advertisers trying to sell to us and, over time, could affect its massive advertising revenue, which totaled $55 billion last year.

"If more users start to feel like they actually are being surveilled through audio, they'll change their behaviors," said Jennifer Grygiel, an assistant professor of communications at Syracuse University. "So even if it's untrue, it could impact the way they use apps and their mobile phone and how they engage in ensuring their own privacy."

Users, for example, might turn off their phones if they're at a personal event, having a private conversation or in a therapy session, Grygiel suggested. They could also be more wary generally and share less information or disable location tracking, which would deprive Facebook of opportunities to learn more about you. They could also turn on ad blockers, which would hit Facebook's revenue.

Already, analysts say, Facebook users are becoming more careful about how much information they give out.

"There's a lot of people who are much more conscious about what they share on social media," said Fatemeh Khatibloo, an analyst at Forrester. "There are people who don't know how to control what they're sharing on social media, so they're not sharing as much."

Poking the conspiracy theory



Forrester put the conspiracy theory to the test, looking at how data flows into the Facebook app when a smartphone's microphone access was turned on and off. Forrester couldn't find any evidence the social network was eavesdropping, Khatibloo says.

CNET reporters also conducted a casual test to see if conversations about specific topics would be followed by Facebook ads about those subjects. We didn't find enough evidence that Facebook was listening to our conversations either.

When asked about the long-running conspiracy theory, a Facebook spokesman pointed to a 2016 statement the social network issued about the subject.

"We show ads based on people's interests and other profile information – not what you're talking out loud about," the statement reads. The social network only accesses your microphone if a user has given the company permission and is using a feature that requires audio, like recording a video, it says.

Facebook's reputation for poor privacy practices only grew worse last year after reports that the social network allowed Cambridge Analytica, a UK political consulting firm, to harvest the data of up to 87 million users without their consent. The data was later used in the controversial UK Brexit vote and Donald Trump's presidential campaign. The reports prompted the Federal Trade Commission to investigate Facebook, which could get slapped with a record-setting fine of up to $5 billion.

Of course, Facebook isn't the only company consumers worry is listening to their most intimate conversations. Earlier this month, Amazon was found to have kept text versions of conversations users had with their Echo devices, even after the voice recordings had been deleted.

And the public is already uncomfortable with the way Facebook and other tech giants follow us around the web. Roughly 68% of consumers say tracking online activity to tailor ads is unethical, according to a survey commissioned by cybersecurity firm RSA Security earlier this year.

Still, Facebook's battered reputation continues to fuel concerns among some users that the social network could be listening in like Big Brother.

"The image of Facebook's lack of privacy puts this veil of concern that's going to be hard for them to shake," said Tim Bajarin, president of Creative Strategies. "They're going to have to do a lot to prove that they are protecting people's privacy going forward."

Freaking people out

The persistence of the eavesdropping rumor has already creeped out plenty of Facebook users, who take to the internet to share their experiences.

In 2016, a man with the user name "Neville" said in a YouTube video that he got Facebook ads for cat food after discussing the topic with his wife. He says in the video that he doesn't have cats and never searched for pet food online. The video has more than 1.8 million views, and people are still sharing eerie encounters in its comment section.

Another user, Isaac Gomez, said he started getting ads for an egg boiler on Facebook after he mulled switching out fried eggs for leaner fare as part of a diet. Some users have quipped they've seen Facebook ads pop up about things they've just thought about in their heads.

Part of the problem, experts say, is that consumers don't completely understand how their data is being used by the company to surface ads. About 74 percent of adults in the US who use Facebook didn't know the social network keeps a list of their interests and traits for ad targeting, according to a 2018 Pew Research Center study.

A Facebook spokesman said the social network is working to provide people with more precise information about why they're seeing an ad and rolling out more transparency tools including on Facebook-owned Instagram.

Facebook has a way for users to understand "Why am I seeing this ad," but some of the explanations are incomplete. When I click on the three grey dots next to a Sephora ad, Facebook says that my email is on a customer list that was collected by Sephora and its partners, or I've provided them with information from Facebook.

Syracuse's Grygiel noted that Facebook isn't telling me exactly what email they're referring to and which companies, other than Sephora, has it.

"They should tell you which one because if you don't want to receive [an ad] based on your email, you should be able to opt out of that," Grygiel said.

Mazur, the photographer, said he still relies on Facebook and other social media sites to promote his photography. After the camera lens ad popped up, however, he started seeing Facebook as a self-interested business, rather than an online hangout.

"It definitely changed my perception of Facebook of being just a fun source to connect with your friends," he said.