OMG WHAT

[arcanetrivia]

Your phone number may have been made public (to some degree) on Facebook without your knowledge or consent (possibly related to friends searching for you with a certain app - if they had your number, it got attched to your profile, kind of thing; it "imported" from them without them intending to do so, by the sound of it). If you have a look at http://www.facebook.com/friends/?filter=pfp you can see phone numbers of certain of your friends - who may or may not have wanted you to know them! See http://www.facebook.com/contact_importer/remove_uploads.php to "unimport" anything that might have been harvested from you. See also the disclaimer on the phonebook page; you need to disable it on the phone too (have no idea how to do this since I don't have one).