If you map some 5-10% of these phone numbers to real users (which facebook can do), then you can map almost all of the remaining phone numbers to their real names as well, using the graph info.
There were some recent papers on algorithms how to do it, and they managed to match ~90% of 'anonymous phone numbers based on the facebook graph data. You stay anonymous only if all your friends and their friends care about anonymity as well.
There were some recent papers on algorithms how to do it, and they managed to match ~90% of 'anonymous phone numbers based on the facebook graph data. You stay anonymous only if all your friends and their friends care about anonymity as well.