that's an issue i've hated about facebook. even if you put their app on your phone, it will download all the phone numbers and then post those numbers in your about - of all your friends and list those numbers as well in your friends about as well. even if they didn't add it. so private numbers are now public. its one of the reasons i don't let it go through my contacts - on any site. they have a tendency to change privacy rules at will, don't tell you about them, and to repair them you have to dig down in to many sub menus.
overall it's best not to do too much with them. they seem to be more invasive than ever when they went public.
---Mike Savad