By FELICIA FONSECA and DAVID A. LIEB
FLAGSTAFF, Ariz. — When vandals sliced a fiber-optic cable in the Arizona desert in February, they did more than time-warp thousands of people back to an era before computers, credit cards or even phones. They exposed a glaring vulnerability in the nation’s Internet infrastructure: no backup systems in many places.
Because Internet service is largely unregulated by the federal government and the states, decisions about network reliability are left to the service providers. Industry analysts say these companies generally do not build alternative routes, or redundancies, unless they believe it is worthwhile financially.