The Associated Press has a report detailing how some police and fire departments are using Twitter to spread information to the public and receive tips on events happening in their jurisdictions. The report also discusses some of the risks that accompany a police or fire department's use of Twitter.
For instance, anyone can currently go onto Twitter as start an account that claims to be a local police department. The Texas attorney general's office has already shut down one such account that purported to be the Twitter account for the Austin police department.
The service is also prone to outages, and was recently hit by a series of worm attacks. With so much about the service out of their control, public agencies might want to think twice before using the service as a public outreach tool.
Still, there are many beneficial ways that public agencies are using Twitter to communicate with the people they serve. Some departments use Twitter text-messages, or "tweets," to notify of traffic disruptions, or to provide information about fast-developing situations like evacuations or school lockdowns.
Agencies also use the service to gather data, not just distribute it. The Los Angeles Fire Department monitors certain keywords on Twitter, and used the service to receive reports of flare-ups and wind conditions during a recent fire.
It's also worth mentioning that the first public reports of the flight that ended up in the Hudson River came through Twitter.
Will the presence of the police on Twitter kill the service? No, probably not. But it does expose some of the issues that the service will have to address as it matures: identity management and reliability being two of the most pressing.