Chapter 7 explores a specific aspect of mosaic searches: information that individuals turn over to private companies. Under the controversial third party doctrine, individuals surrender all Fourth Amendment rights when they share information with a third party. Most legal scholars criticize the third-party doctrine as anachronistic and a significant threat to privacy. This chapter will argue that the conventional wisdom is wrong, for two reasons. First, modern information sharing enhances our privacy; thus, some aspects of the third-party doctrine can be classified as reactive surveillance. But more importantly, the cost–benefit analysis theory reveals that this massive private collection of data is a positive-sum shift in surveillance. On the privacy side, corporations themselves can assert their own Fourth Amendment rights to keep this information secret – a phenomenon we are already seeing in many technology companies that store and transfer our data. On the security side, millions of companies are constantly collecting billions of pieces of data, all of which can be available to help solve crimes when the government can meet the appropriate standard to overcome the companies’ Fourth Amendment rights.