Business starts with trust, which is why, when PETCO.com opened for business in 2001 to sell pet supplies to consumers, it made some reassuring promises. “At PETCO.com, protecting your information is our number one priority, and your personal information is strictly shielded from unauthorized access,” the Web site said. It also said, “Entering your credit card number via our secure server is completely safe. The server encrypts all of your information; no one except you can access it.”

If only that had been true.