Adding one more to its long list of security flaws, users reported that Facebook has been posting their phone numbers online, making it easy for unknown persons to contact them directly. If you have updated your number on Facebook profile or synced the site with your phone contacts, your number will appear on Facebook.
The recent flaw was buzzing on Facebook and many users posted messages on their walls saying, "All the phone numbers in your phone are now on Facebook" asking others to delete it for security reasons.
Meanwhile, Facebook rejected the claims saying that the feature has existed for over a year and the phone numbers were added by users or their friends. It also said that the mobile numbers will be visible only to the user.
"Rumors claiming that your phone contacts are visible to everyone on Facebook are false. Our Contacts list, formerly called Phonebook, has existed for a long time. The phone numbers listed there were either added by your friends themselves and made visible to you, or you have previously synced your phone contacts with Facebook. Just like on your phone, only you can see these numbers," Facebook said.
If you want to check the phonebook, Login to your Facebook account > Click on 'Account' > Click on 'Edit Friends' > Click 'Contacts'. You can see your friends with their phone numbers! (shocked?)
If you would like to remove your mobile contacts from Facebook, you need to disable the feature on your mobile phone or Click here.
Anyhow, Facebook says, "Imported contacts are displayed on your Invites and Imported Contacts page and synced mobile contacts are displayed in your Facebook Phonebook. Contacts may be used to improve the quality of friend suggestions for you and your friends."