Facebook’s “People You May Know” has always been an interesting algorithm to watch in action. While we can’t claim to have analyzed its function in-depth, it’s fascinating to see how the addition of a single friend can change the people Facebook thinks you might like to follow. Add a few high school buddies, and you’ll see more of your fellow graduates. Add a business contact or family member, and the same thing happens.
A recent investigation by Fusion.net found that Facebook doesn’t just prowl your phone contacts or mutual friends to find potential suggestions. The company also uses your location data to match you with other Facebook users, unless you’ve specifically configured your smartphone not to share that information.
A Facebook representative told Fusion: “We show you people based on mutual friends, work and education information, networks you’re part of, contacts you’ve imported and many other factors.” Simply being in the same location as another person isn’t supposed to trigger a “PYMK” notification, but the Fusion story discusses the case of a parent who attended an anonymous group meeting of parents with suicidal teenagers. The next morning, Facebook suggested that one of the other anonymous parents at the meeting was a person that the first parent might know. None of the parents in question had exchanged any contact information, and while Facebook claims that the two individuals must have had some other network in common, the episode highlights just how much data the company scoops up on its user base, as well as how little we really know about what the company does with that information.
Ongoing research into the so-called “six degrees of separation” has confirmed that the gap between two random people is often much smaller than you might think, which means it may not be particularly difficult for Facebook to find a common network between virtually any two people. Without knowing more about the company’s practices it’s impossible to know how two people attending the same anonymous event, neither of whom knew each other previously, wound up being matched together.
Earlier this month, we wrote about Facebook’s aggressive use of location tracking as part of its new mobile advertising rollout. Going forward, Facebook will tell advertisers if their local ads drive additional foot traffic to stores and share aggregate demographic information on the customers in question. Obviously a feature like this can’t work if you don’t enable location services or connect to WiFi, which is why Facebook’s iOS and Android clients recommend leaving location services enabled.
The fact that two people who attended a deliberately anonymous meeting were “outed” to each other on Facebook is one small example of how continually chipping away at user privacy can have significant real-world consequences. Just because you visited a bar, went to a concert, or saw a movie doesn’t mean you’re interested in being friends with every single person you shared the experience with. People seeking treatment for mental or physical illness may not be interested in meeting people who share these traits, or may simply wish to keep their private lives private.
At its best, Facebook’s PYMK is a useful way to find old acquaintances or friends you’ve lost touch with. But there are risks associated with simply smashing people’s profiles together based on unknown network linkages and proximity to one another. We recommend disabling location services for Facebook unless you absolutely need to leave them on. There’s no reason to hand the company a comprehensive record of where you go and when you went there.