Ask HN: FB suggests friends after visiting same city, don't use FB phone. How?

36 points | by shafyy 35 days ago


  • etempleton 35 days ago

    You are missing the most obvious and most likely reason for matching with new coworkers. Your new coworkers searched and viewed your profile on Facebook after meeting you. This is a key way Facebook suggests friends.

    • doopy-loopy2 33 days ago

      this. so obvious yet we jump to conspiracy.

      • DudeInBasement 32 days ago

        It's so obvious that it's reptiles, yet we jump to a simple search on Facebook.

    • dnh44 35 days ago

      It could be WhatsApp but I think it would be trivial to figure this out any number of ways.

      You have a Facebook account, if you don’t check it on your phone presumably you do on your notebook or desktop. You probably browse the internet at home from the same WiFi network with both your computer and phone. Different cookies from the same IP address would indicate the same household. It wouldn’t take a lot more to know they belong to the same person. IP addresses can strongly correlate with a geographic area.

      Since nearly every website has those social media buttons Facebook can track you from site to site even if you’re not logged in.

      For sure Facebook knows where you live and has matched up your facebook-free phone to your Facebook account.

      I’ve got no experience with actually doing any of this, it’s just what seems obvious to me. I’m sure the whole truth of it is much scarier.

      I haven’t had a Facebook account in over a decade but my current girlfriend had my ex-girlfriend from 15 years ago pop up in her recommended list. We live about 10,000 km apart.

      If there are any Facebook engineers reading this I must salute you. Your work is amazing.

      • arcturus17 35 days ago

        I used to date girls on Tinder with at least a few degrees of separation (ie, no friends in common), didn’t have Tinder and Facebook connected in any way, and the dates would still show in my friend recommendations list.

        It was WhatsApp.

        • sopromo 35 days ago

          I think that your example is not correct.

          Tinder and a lot of others apps share information with Facebook about what you do by using their SDK.

          • arcturus17 34 days ago

            How would they do that if I didn’t log in with Facebook or in any way connect the apps together?

            What I did do is add those girls’ numbers on WhatsApp - which is a Facebook property - and they suddenly appeared as friend recommendations.

            But if there is any definitive proof it’s that I only was recommended the ones that I had messaged on WhatsApp, never those that I had only chatted up on the Tinder app...

            • sopromo 34 days ago

              Each phone has an unique advertisement identifier, they could link you across several apps with that.

              But it may be very possible that they do a combination of everything to track you (whatsapp, instagram, facebook, oculus, apps that use the sdk...)

        • lacker 35 days ago

          My guess is phone number matching. Your friends use Facebook on their phone and added your contact information recently. That’s enough for Facebook to figure out that it’s a potential match, given that you already have some friends in common.

          • readyoursicp 35 days ago

            Is it possible your friends searched you up?

            • netsharc 34 days ago

              Did you add each others' numbers on WhatsApp?

              Or if you moved due to work and you got added to a company-wide address book which is also synced to employees' phones and in turn got synced to WhatsApp, Facebook's systems could probably match up names to suggest a connection.

              Although, why only these 2 people and not others from the company? Scarily there's probably enough data between you 3 for FB to know that you would be compatible with each other, so maybe Facebook figured the same thing you 3 figured out in real life -- you hung out with each other so I would deduce you found these 2 co-workers interesting. But I doubt anyone got paid to make such sophisticated stuff, there's probably a simpler logic that offers a quantity but not quality of "friends".

              I still want to write a short story that starts with a guy saying "OK Google, get me a girlfriend", and an algorithm that slowly pops up suggesting events and locations for him to visit, knowing that a girl that he'd be compatible with will be at the events/locations...

              • codegeek 35 days ago

                You visit a website and if they have fb pixels/tracking, it is very easy. FB is everywhere, EVERYWHERE.

              • NVHacker 35 days ago

                Download your FB information and scan through it. If you can, ask your colleagues to do the same. FB tracks the websites you are visiting so the local comedy club website is a possibility.

                • aminozuur 35 days ago

                  If I create a brand new Facebook profile, and I never tell Facebook my location (neither via my browser geolocation or profile info), however most of my Facebook friends that I chat with daily live in a town called Hackerville. I've never installed or used Instagram or Whatsapp.

                  Guess where Facebook thinks I'm living?

                  They can be pretty sure I either grow up or live in Hackerville.

                  • winrid 35 days ago

                    FB could buy your data from other networks, provided via some other app.

                    Also your coworkers probably looked at your FB profile.

                    • netsharc 34 days ago

                      This freaking sucks, I use one "for junk" email address for online shops, etc, but it's also the email I use for Facebook. Facebook opened its "Data Disclosure" section a few months ago, and mine had a list of many companies which uploaded their customer data to Facebook and probably could target me...

                    • beamatronic 35 days ago

                      I think even your cell phone location data by IMEI is available for sale these days.

                      • ta17711771 34 days ago

                        Journalists etc have purchased it reliably for like...$300 if I recall correctly.

                      • mifreewil 35 days ago

                        It’s really impossible to know without more info, as people have mentioned you can download your fb info for some clues. One possibility I haven’t seen mentioned is they are using your credit card data that they’ve purchased.

                        • parliament32 35 days ago

                          Either WhatsApp or Instagram.. all FB properties share a common user graph. Or your friends searched for you on FB.

                          • vopi 35 days ago

                            I suspect it's through a Bluetooth beacon. Basically analytics/trackers for physical stores.

                            • joemazerino 35 days ago

                              Sounds like WhatsApp and/or your phone number connecting the dots.

                              • thinkingemote 35 days ago

                                Local comedy club plus shared friends.

                                • dralpha7 35 days ago
                                  • MintelIE 35 days ago

                                    Voice recognition, cameras always on and recognizing, could be a million things.

                                    • yolomcsuperswag 35 days ago

                                      My guess is WiFi-triangulation by WA. Just a guess, though.