Wireless carriers are surreptitiously tracking your location, and selling the data to other companies (in addition to supplying it to the government):
"But what these services show us is even more alarming: US telcos appear to be selling direct, non-anonymized, real-time access to consumer telephone data to third party services — not just federal law enforcement officials — who are then selling access to that data. Given the trivial “consent” step required by these services and unlikely audit controls, it appears that these services could be used to track or de-anonymize nearly anyone with a cell phone in the United States with potentially no oversight."
https://www.techdirt.com/articles/20171017/11071138421/wireless-carriers-again-busted-collecting-selling-user-data-without-consent-opt-out-tools.shtml
"But what these services show us is even more alarming: US telcos appear to be selling direct, non-anonymized, real-time access to consumer telephone data to third party services — not just federal law enforcement officials — who are then selling access to that data. Given the trivial “consent” step required by these services and unlikely audit controls, it appears that these services could be used to track or de-anonymize nearly anyone with a cell phone in the United States with potentially no oversight."
https://www.techdirt.com/articles/20171017/11071138421/wireless-carriers-again-busted-collecting-selling-user-data-without-consent-opt-out-tools.shtml