How does Facebook's "People you may know" feature work?

To be honest I've never really looked closely at this part of the Facebook site (I hardly even log on any more) but out of curiosity I had a look tonight and it freaked me out. I use a personal email address for Facebook and it's not linked to my business email at all, yet scrolling down the list of people I "might know" I found upwards of 100 people who have been customers of my business over the last 12 years or so. Some of them I literally haven't heard from for 12 years, and they certainly never had my personal email address or anything that could link them to my Facebook account (FB didn't even exist back then). My Facebook account is pretty much locked up privacy wise and there is nothing about my profile pic, cover pic or anything else visible publicly which could link me to my business and there are a ton of people with the same name as me in New York. The only thing I can think of is that these customers from years ago have for some strange reason tried to find me on Facebook and a link has been made there. Or the Facebook phone app has pulled out my phone number and linked it to other people who use the FB app and still have my phone number saved in their phones after all these years. Very sneaky if so!  But man, scrolling down that list had me yelling "holy s***" over and over again. 
 
The order freaks me out as well. It's  a 100 or so ancient ex-customers I haven't heard from in years, and then the expected "friends of friends." It's like Facebook is saying "Hey, before we show you the people you'd expect to find, have a look at these people from your past who have absolutely no digital connection to anything that's linked to your Facebook account! There, that blew your mind didn't it!" 

It searches for third cousins four times removed and gets anyone closer than that...in most cases.

I tend to do the opposite of what it wants me to do.... instead of adding  "People you might know"... I periodically remove people I do know.  I also go through my "friends" list and evaluate each one..... do I actually know this person in real life..... are they contributing interesting points of view in an intelligent way....... if not.....  Culling the herd. And I rarely accept friend requests from people I have never met in person anymore.

Hi,
 
I rarely use it and in general, I do not use any of those friendship and brouhaha sites!
 
I have never trusted their security levels, and the fact that they want more information about you. Not that I have anything to hide ... not gay ... 64 ... didn't bop the prom queen like everyone else did ... you know ... the usual fanfare!

sharke
I made a point of not allowing it access to my contacts lists when I signed up.

Good for you. Apparently some of the people you might know missed that opportunity. 

I think it shows you friends of people you have as friends... makes me wonder about some of them. Where do they get these big eyed oriental girls with two posts? Why do they think I may know them?? Why do they think I would WANT to know them?
 
It is weird sometimes. Facebook creeps me out.
 
J