Just how much personal information does phone metadata reveal?

"Stanford University Ph.D. student Jonathan Mayer and his research partner created an Android app called MetaPhone that asked users to volunteer their phone records in an effort to learn what could be uncovered from metadata. More than 500 people signed up.

"We began by ID'ing the organizations associated with the phone numbers in our dataset. We did that primarily by using phone books provided by Yelp and Google. Totally public. Totally easy to access," Mayer told CNET's Sumi Das."