A system built on millions of cell relays, antennas, and sensors also offers previously unthinkable surveillance potential. Telecom companies already sell location data to marketers, and law enforcement has used similar data to track protesters. 5G will catalogue exactly where someone has come from, where they are going, and what they are doing. “To give one made-up example,” Steve Bellovin, a computer-science professor at Columbia University, told the Wall Street Journal, “might a pollution sensor detect cigarette smoke or vaping, while a Bluetooth receiver picks up the identities of nearby phones? Insurance companies might be interested.” Paired with facial recognition and artificial intelligence, the data streams and location capabilities of 5G will make anonymity a historical artifact.