Cell phone networks were clogged and callers had a hard time getting through after the Virginia/DC earthquake today. As we have seen in other disasters, don't count on the ability to use your cell phone after a major disaster. Even though this earthquake didn't bring down any cell towers, the volume of "Did you feel it?" calls quickly overwhelmed the cell phone network capacity.
This points out the need to have a plan that will allow you to respond to a disaster even if you can't use your cell phone to communicate for hours or days. This may mean having a predesignated meeting place or an alternative contact in case of an emergency.