I'm signed into Plug.dj with my Twitter account, which knows I'm in South Africa. We're in the same room on Plug.dj. This is why I'm scared of the lack of internet privacy sometimes.
I made a Facebook account, and I only added my name and my current address, which is half the country away. Some time later, they recommended me my whole family and people I knew from senior high school as friends.
I don't own a facebook account, but because I recently made myself a new professional email that I can put on applications I have a google+ account.
My parents have a facebook account though and my mom claimed she got some kind of automated you might know this person thing through facebook with my friend's completely unused facebook account he was pressured to get for his job.
The only indication I have that I know that person is that they are a contact I set as always important in my gmail, and even then only for my main email account which was signed up for well before google+ back when Gmail was in Beta, that I still refuse to create an account for.
So the information somehow went from my gmail to an alt account's google+, then SOMEHOW to the facebook network(I thought they were competitors), somehow linked the email address with my friend's real name, and then sent some kind of automated friend request to my parent's facebook account (I guess maybe because we share an address? Hell if I know).
You can not escape the facebook. It knows you better than you know you.