You know what is even more hardcore than facebook with the "friend finder?" Freaking linkedin. That thing found people I sold things to on craigslist in 2005 and put them in my "people you may know" suggestions. Girls I hooked up with in high school, a professor who taught a course randomly during an off summer at a community college. People I've emailed from my fake throwaway email accounts I don't remember the logs ins or the passwords to any more. People I've only corresponded with from my firewalled work accounts and never logs into them from my personal computer. Old frat brothers who were 4 years ahead of me in college. A person who went missing when their family moved away from my jr high school and I completely forgot about them. My Japanese exchange student who I lost contact with in 2008. People from random 4-wheeling forum I never emailed with or talked to directly. I have no idea how they did it but it was rather disconcerting. If I knew how to turn it off, I would.
I seriously don't know how Linkedin found all these people but they somehow dredged them all up.