Facebook reads and saves all numbers stored in phones of members using any FB mobile phone app. This includes all numbers stored on the phone, obviously including those of FB non-members. This feature is actually live since February 2010, when it caused some concern. Yes, these numbers are not visible to the public, as is Facebook's **standard excuse** for its intransparent mining of data. But the database matching your name and your phone number plus the connection to an FB member is owned by Facebook and it will be mined at will. Your number and related records will thus be conveniently fitted into the social graph and monetized in whatever way FB sees fit. Yes, even if you're not on Facebook. As with the photo tagging without consent “feature”, Facebook is using you as a proxy to collect your friends' data, without heeding their privacy concerns, for FB's own monetary interest.
Dirk Dot Net
Creator of useful things. Based in Chiang Mai, Northern Thailand.