According to Fox News, though Facebook argues that the feature has existed for over a year, its users are now realising the sensitive information they're sharing, and are buzzing up a storm. For some, it's one sting too many from a company they're growing reluctant to trust with their data.
"That might be the last straw," wrote one worried Facebook user.
"All my friend's personal phone numbers are on there! Not happy," another complained.
Facebook adamantly denied that the confidential phone numbers of friends and family are freely accessible online, as many have worried.
The company posted a statement in which it said: "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."
Don Debolt, director of threat research for Internet security firm Total Defense, said: "In some ways, Facebook is attempting to be very helpful, but how exactly they are using this information isn't exactly clear."
The real concern for many is the world of underage children on Facebook - as many as 7.5 million kids under the age of 13, despite the company's official prohibition on those under 16, and 5 million under the age of 10, according to one recent survey.
"I think this is a wake-up call for sure for parents to get involved," Debolt said.
A new survey conducted by NPD Data and Comscore for Social Shield found most parents admitting that they don't have the tools, knowledge or time to properly monitor their children on social networks - and many admit that they take no precautions at all.