SAN FRANCISCO (AP) — With every phone call they make and every Web excursion they take, people are leaving a digital trail of revealing data that can be tracked by profit-seeking companies and terrorist-hunting government officials.

The revelations that the National Security Agency is perusing millions of U.S. customer phone records at Verizon Communications and snooping on the digital communications stored by nine major Internet services illustrate how aggressively personal data is being collected and analyzed.