The first and last must just be geolocation based, right? Like, these two people are in a room together every X day for Y hours... they probably know each other.

The sperm donor guy, though... facial recognition? No idea.

There's gotta be more to that sperm donor story. "Oh that must be my biological kid from that sperm bank trip 20 years ago" is not the natural train of thought when you see someone who maybe vaguely looks like you as a suggestion on Facebook. And whatever the other context was - maybe one of them searching for the other - probably gave Facebook what it needed to make the connection.

Data bought from 23AndMe ?

> The sperm donor guy

How did the Sperm Donor know it was his child?

Find that and that's how Facebook knows.

To look at a friend suggestion and know it's your child means you have been in contact with someone past the donation stage.

Nothing about how Facebook offers suggestions are secret to my knowledge.

All that's happening is people are not aware how easy it is to find information from networks

More likely adress book / phone contacts import.

The geo thing is really happening.

I also have the theory that they are using WiFi names / AP MAC addresses as well. If you happen to be connected to the same private WiFi network, you probably know each other.

Facebook has a patent for using dust and scratches on photos to track which camera they came from. But they claime(d) not to be using WiFi or Geolocation for the PYMK feature - https://gizmodo.com/facebook-knows-how-to-track-you-using-th...

Based on the track record of other Facebook claims of the "we don't do X" type, this is basically proof that they do and/or did do both of these things. Maybe "accidentially" and "unintentionally" ;-)

Which is one big reason why the only sensible way to use Facebook on mobile is to delete the app and use only a browser, while keeping your location sensors turned off.

There is a nice app called Frost that is basically a wrapper around the web interface with convenience features, and is free (i.e., available on F-Droid).

As one of the factors probably, but they don't recommend random people who are nearby. There has to be some actual connection (friend-of-friend, address book, in the same group etc.)

> but they don't recommend random people who are nearby

I think that's probably true. You need to spend sufficient time near someone--like within a few feet or so.

I had an interesting experience where Facebook recommended me as a friend to someone I sat next to on an airplane, with whom I had a conversation with. My phone was in airplane mode. Not sure how that happened, TBH!

They probably looked you up afterwards on Facebook or another site using Facebook analytics.

It could be based on connecting to the same in-flight WiFi.

And you might be able to correlate seating with WiFi strength? :)

so a stalker will get recommended to a 'stalkee' ?

I mean, part of the use case there is that the 'stalkee' will at least be notified that the person s/he has seen four or five times is definitely stalking them. So that's good, I guess.

This post is obviously sarcasm.

Happened to me a few times, some people I randomly met in a bar where recommended to me the next day, super creepy.

Could not be because they checked you out by name on facebook?

Possible, although I've only given them my first name. And this is not just on one occasions, it has happened multiple times. My best guess has always been that Facebook uses some geo targeting to see who was at the same location at the same time.

There’s no need to speculate - the article we are commenting on informs us that happened through email contact sharing.

In the recent events, like https://news.ycombinator.com/item?id=22178917 we have learned that there is a lot of data moving around, including various third-parties.

I see those as BIG pieces of information! The number of people that I "might know" because we've exchanged email with the same person is horrifying in this context. There's a dystopic story to be written (which often means it already has been) about law enforcement using this second-order conntection as Reasonable Suspicion, a "why did we find your business card in this bad guy's wallet?" connection.

This is not a dystopian fantasy; it's exactly how intelligence agencies map out terrorist groups' and foreign militaries' structures online. Israel is supposedly particularly good at this kind of analysis, but I'm sure other countries are doing it.

You have to wonder what kinds of non-employee access are a part of the Facebook web application. That is, perhaps Israel's edge is that they have an (made-up) Investigator version of FB when they log in.

I figure everything down the left aside on FB corresponds to a permissions bit for each entry, so maybe some classes of user get some really fun items over there.

And all the "males of fighting age"

We can get heuristics with lower false positives these days.

But we don't know if these are false positives. The connection between all those examples doesn't have to be the suggested link. E.g. the patients could be suggested because they have a common friend.

Yeah, the psychiatrist seems the easiest to explain since when choosing a medical professional people may ask their friends who they recommend.

> Yeah, the psychiatrist seems the easiest to explain since when choosing a medical professional people may ask their friends who they recommend.

IIRC, connections like those were often explainable by addressbook data. Please assumed Facebook didn't have access to that when it actually did (I'm pretty careful about this kind of stuff and found mine had been slurped at some point, for instance). It's not inconceivable that a psychiatrist and patient may have exchanged emails or phone numbers.

Since the system is both aggressive and intentionally opaque, it doesn't much matter to me whether the positives are false or true. If Facebook would like people not to feel threatened by it, then they could either not do it or make it much clearer what's going on.

I mean, they're creepingly good sometimes. I once met a lady in the streets, we exchanged numbers and sent a few messages but never saw each other again. Facebook recommended her to me. I used whatsapp to text her, so I assume Facebook crossed some data and suggested her to me.

Relatedly, Venmo has given me the identify of people I've contacted before by phone.