TCS has a recent article on using Smart Mobs for homeland security:

We learned on 9/11 about the effectiveness of individuals who were empowered by personal technology.

...

The market research firm Telephia estimates that 53 percent of urban Americans now have mobile phones. However, the Homeland Security program has failed to capitalize on that private sector resource to deliver actionable information when and where people can use it, which would both lessen the demands on first responders and help people avoid panic because they feel they know what to do and have the real-time information they need.

...via Scripting News