Caleb Chen:

American telcos like AT&T and Verizon sell your personal information: home address, phone number, and cell phone contract details, possibly even down to your current longitude and latitude, to anyone with your mobile IP address. This means that when you use your mobile to browse the internet, each of the sites you visit could easily have your full name, phone number, home address and email address, and even approximate location. AT&T has been actively providing this information to law enforcement for over a decade, also for a profit.

Looks like I’ll switch to VPN on cell networks.