[__z]

Facebook doesn't only know what you are telling it - Facebook knows a lot about you even if you don't have a Facebook account. They create "shadow profiles" of non-users through info about you your friends give to Facebook. They may also track non-users through Facebook beacons and "like" buttons placed on other sites.

Plus Facebook can very trivially figure out where you work without you telling them. Let's say a colleague lists they work at Initech. They then create a group called "co-workers" and add you to it. Now Facebook can do some very simple datamining and figure out you work at Initech. You betcha they do that.

Even if you don't have an account and browse the web like RMS, you still probably have a shadow profile unless you have no friends. If a friend gives the Facebook app permission to view it's phonebook (typical) and you are in it now Facebook knows and stores everything about you that's in your friend's phonebook - name, email, phone number, possibly home address, etc. This is one way it creates shadow profiles.

Facebook has face recognition software - need I say how much they can gather about you if your friends post pictures of you online?