Apple and Google have further refined the ability of the cellular platform to track user location through a form of “crowd-sourcing.” Individual cell phones report signal strength and location measurements for cell towers and WiFi access points.This data creates a map of radio sources that can be used to rapidly locate a cell phone user. Fine-grained location data enhances location-based services, but also creates a substantial privacy problem — location data at the level of individual addresses can reveal a great deal about the beliefs, preferences, and behavior of the subscriber. The harm that may occur through marketers’ use of such data is considered through an exploration of the philosophy of place. The ability of marketers to de-anonymize location traces is then considered in detail through a unicity distance analysis. The unicity distance results are used to identify effective techniques for exploiting location-based services while maintaining anonymity.