An anonymous reader writes: It goes without saying that cellphone carriers have access to tons of data about their subscribers. They have data about who you call, what sites you visit, and even where you're located. Now: "Under the radar, Verizon, Sprint, and other carriers have partnered with firms including SAP to manage and sell data." The article describes some of the ways this data is used by marketers: "The service also combines data from telcos with other information, telling businesses whether shoppers are checking out competitor prices on their phones or just emailing friends. It can tell them the age ranges and genders of people who visited a store location between 10 a.m. and noon, and link location and demographic data with shoppers' web browsing history. Retailers might use the information to arrange store displays to appeal to certain customer segments at different times of the day, or to help determine where to open new locations." Analysts estimate this fledgling industry to be worth about $24 billion to the carriers, and they project huge growth over the next several years. The carriers are trying to keep it a tightly held secret after seeing the backlash from the public in response to government snooping, which involves much less private data.