I live in hurricane alley (South Florida). You would be shocked how many of my neighbors had no phone service during the last big storm because electrical power was down. The phone lines were good, but everyone had cordless phones that require electrical power at the base transmitter in order to operate. A simple POTS wired phone available for less than $10 at Wal-Mart would have been a salvation. I keep one permanently connected to the phone line in case of failure and a stored backup in case of a long term power failure. And has been stated, if you have Vonage or other broadband based telephone service, it will die as soon as your router dies from lack of electrical power. If you plan on having phone service during a blackout and have ditched POTS for an internet phone service, you need to be prepared to provide backup power to your router and cable or ADSL modem.

Craig