If you use facebook on your cellphone, chances are, every phone number stored in your phone has been ripped to facebook. To see if it is true, got to account > edit friends > contacts. It will show you all the numbers taken from your phone.
I found this out by accident trying to change my cousins account setting for her. I don't even own a cellphone, so mine was empty save for my facebook friends that use facebook mobile all the time. Her contact list had every single phone number there, including people that don't use facebook.