Facebook’s Friend Suggestions
Facebook is the largest social networking site, with over a billion monthly active users averaging hundreds of friends. For a few years now, Facebook has had a feature that recommends friends to users. While the idea of recommending someone new friends may seem strange, chances are you actually know the person being suggested. No, Facebook is not a magical being that predicts who you know in real life (sadly). Instead, it uses the power of your network, as well as your perceived strong ties and weak ties.
One way Facebook finds suggested friends is by looking at the number of friends in common. There’s no coincidence that this user with 150 mutual friends is showing up as a suggested friend. Facebook uses its large database to check who you might know in real life by looking at those who you have the largest number of mutual friends with. Chances are if you have over 100 mutual friends with someone, you at least know they exist. The other way Facebook suggests friends is by looking at those who you have strong ties with. Strong ties are found by seeing who you interact with the most, either via chats or wall posts. If 10 of your best friends are mutual friends with a user, there’s a high chance that your friends have introduced you to him at some point or another. On the contrary, if 10 random friends of yours are mutual friends with a user, there’s no guarantee that you’ve ever seen this person ever before in your life. Facebook incorporates the theories of strong triadic closure to find the users who you are most likely to know based on your current connections.
https://www.udemy.com/blog/how-does-facebook-suggest-friends/