This is an interesting article about the DHS monitoring social networks during the 2010 Winter Olympics. I believe we will see more of this activity since it gives those in public information positions a portal into what may be going on in an area of interest.
The important point here is not that the DHS is monitoring information; it is the opportunity for all of us to develop relationships and areas of interest we can monitor during an incident. All groups could benefit from sharing information (albeit not always factual) including businesses, schools, churches, and communities. One great way to share information as an alternate to other methods during an emergency is Twitter or Facebook.
As required by law, the DHS has published a Privacy Impact Statement about its monitoring activity--in this case monitoring social media outlets for security reasons for the Vancouver Winter Olympics. the full article is available at: http://www.emergencymgmt.com/emergency-blogs/crisis-comm/DHS-Monitoring-Social-Media.html