On Wednesday, the largest wireless carrier in the United States, Verizon, announced that they will now use information they collect about the websites you visit, the apps you use and your location to "create business and marketing reports" and to "make the mobile ads you see more relevant."
In a statement regarding the privacy change, Verizon says, they will also share your location information with other companies so that these third parties can "create business and marketing reports" about things like the "number of mobile users who take a particular highway during rush hour."
While all Verizon customers are subject to the changes, those who don't want their information shared can choose to opt-out on Verizon's website. If you choose to remain opted-in, Verizon says that none of the information they use or share will be able to be personally identified as yours.
The FCC's rules on mobile privacy assert that mobile carriers must get permission from customers if they want to use your information for marketing purposes unless it's for "enhancements to services you already use."
According to the Los Angeles Times, "every carrier stores these types of data," although how long they retain customer data varies by provider.
A Department of Justice study comparing amount of time various carriers retain customer's information found a wide variation among the companies examined. For example, Verizon saves text message content for 3-5 days while Virgin Mobile saves it for 90 days. But it's Verizon that stores your website browsing history for the longest. They keep it for a full 90 days, as opposed to 60 days for Sprint. T-Mobile and Virgin Mobile don't save web browsing history at all. Visit the ACLU's website, where you can see a full version of the Justice Department's report.