“Behind the Facebook profile you’ve built for yourself is another one, a shadow profile, built from the inboxes and smartphones of other Facebook users. Contact information you’ve never given the network gets associated with your account, making it easier for Facebook to more completely map your social connections.”
I have a hunch if people knew how Facebook actually works, they’d be more concerned about it.
Gizmodo pulls back a bit of the curtain in this explanation of how Facebook figures out everyone you’ve ever met.
It explains how Facebook uses the access people give it to their contacts and address books to map massive amounts of data that reveal connections you may not want revealed.
As one security expert reveals, “Mobile phone numbers are even better than social security numbers for identifying people.”