another random user (2645241)
writes "A researcher by the name of Suriya Prakash has claimed that the majority of phone numbers on Facebook are not safe. It’s not clear where he got his numbers from (he says 98 percent, while another time he says 500 million out of Facebook’s 600 million mobile users), but his demonstration certainly showed he could collect countless phone numbers and their corresponding Facebook names with very little effort.
Facebook has confirmed that it limited the Prakash’s activity but it’s unclear how long it took to do so. Prakash disagrees with when Facebook says his activity was curtailed."Link to Original Source