Didn't Zuck want to start a dating service? With all the data they could probably match up people quite well (including their geographical closeness). FB could even have data on what kind of people you find attractive, based on how much of someone's photo album you went through and how long you admired their selfies.

Netflix was famous for its recommendation algorithm, a big-data dating service might even be able to see that a lot of couples work if one liked movie/song/city X and the other liked Y.

In theory, FB/Meta could also monitor the progress of relationships, from the "X added you as a friend on FB/Instagram", through the increase of communication between each other (WhatsApp messages, calls), to seeing each other (geo-location at different bars, restaurants) and even spending nights at eaxh other's places (which WiFi network was your phone connected to, throughout the night).