David Stephenson posts a useful series on disaster management on YouTube here. This video takes a look at the uses of Twitter in an emergency. Twitter was used to good effect by the Los Angeles Fire Department and the American Red Cross during last summer's wild fires in California. Universities are exploring its use as a tool for emergency notification in the event of major incidents (which seem to happen all too often in U.S. schools). There are also lots of possibilities for companies with dispersed work forces to use it for emergency activation and high interest information sharing.
Take a look.