There are now sites where all you have to do is upload a clear image of someones face and you can then find their social media accounts as well as any photos of them online...
Take for example this website:
https://facecheck.id/
It is completely free.. So I gave it a shot myself.
I found an image on my phone that I never posted online, uploaded it to the site, and patiently waited as it did whatever magic it did... like seriously what kind of code went into making this thing. It blows my mind!
Anyways, after it was complete, sure enough, it had found my linkedin, instagram, an old reddit account I had posted some photos of myself onto the r/beards subreddit. It found my entire online identity as well as photos of me on Pinterest!! I have never used Pinterest in my life. I was shocked..
I was a little tempted to test it with other people in my life but it honestly was just a bit too creepy and I think I don't really want to know.
This site and others are surely being used by malicious actors blackmailing every day folk. It's also probably being used by companies looking to do a little background research on prospective employees before hiring them.
I forgot to mention that it will also find a bunch of people who look extremely similar to you, so while it does have some false positives, it will work - you just have to do a little bit of scrolling to sort through your lookalikes.
Moral of the story is be careful what you put online.. especially these days. Also might be a good way to find all your images online so you can go through and clean up your online presence.