You may recently have gotten worried that Facebook has your phone number, even though you don't remember giving it to the social network. At the same time, you may have also realized the social network actually has your Facebook friends' phone numbers too, and you can see them.
Even though this feature has been available for quite a while, it became a big deal this week when some users started posting this message on their Facebook status, which in turn was showing up on people's News Feeds:
Friends! "ALL THE PHONE NUMBERS IN YOUR PHONE are now PUBLISHED on Facebook! Go to the top right of the screen, click on Account, then click on Edit Friends, go left on the screen and click on Contacts. Then go to the right hand side and click on "visit page" to remove this display option. Please repost this on your Status, so your friends can remove their numbers and thus prevent abuse if they do not want them published."
This is a little over the top, but it did freak out a lot of people who weren't aware Facebook had their number, and that they could see all their friends' numbers too. You can see this list yourself by clicking on Facebook Phonebook (you must be logged in to Facebook). Palo Alto has essentially aggregated the numbers that all your friends have shared with you into a list: you can see the individual numbers as well by going to each of your friends' profiles.
"Rumors claiming that your phone contacts are visible to everyone on Facebook are false," a Facebook spokespers said in a statement. "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."
So if Facebook didn't take your number by force, when did you give it to the social network? You could have put it in manually (Edit My Profile => Contact Information => Phones). If this is the way you added it, then this is also the way you should remove it. If you'd rather keep your phone number on Facebook, you can instead restrict who sees it (Account => Privacy Preferences => Customize settings => Contact Information => Your number). You have the following options to choose from: Everyone, Friends of Friends and Networks, Friends and Networks, Friends of Friends, Friends Only (this is what I have mine set to), and Customize (which lets you drill down to specific people).
The other possibility is that you have installed the Facebook Mobile app on your smartphone at some point. After doing so, there was an option to sync your phone contacts with Facebook. This allows you to call Facebook friends without knowing their number as well as seeing their Facebook profile picture when you call them or they call you. This is possible because Facebook compares the number you have for your friend Joe Smith with the number Joe Smith has on Facebook.
Here is what the message looks like:
In other words, you agreed to upload information on your phone to Facebook and your friends have done the same, so they can see your number(s) and you can see theirs. If you want to stop this from happening, click on Remove Imported Contacts (again, you must be logged in to Facebook). On the Remove page, Facebook says, "Before you click Remove, you need to make sure syncing is switched off" and gives instructions on how to find syncing on your smartphone.
Here is where it gets a little worrying: this list includes the phone numbers of your friends who are not on Facebook. For example, if you let Facebook grab your phone's contact list, which includes a Joe Smith who isn't on Facebook, the social network still gets whatever you had about Joe on your phone (his first name, his last name, and his phone number). Facebook says it does this so if Joe one day joins the social network, it will suggest that you become Facebook friends.
Facebook is once again going out of its way to be helpful, which many users like a lot and others simply find scary. Putting all your phone numbers together in one place is part of the company's bigger strategy to become the center of all your communication needs (just this week the company released a new Facebook Messenger app for Android and iPhone).