From Wikipedia, this (heavily cited) example of Twitter's usefulness should sell it to you, or not:
Twitter is being used in creative and important ways as a social justice tool to connect groups of people in critical situations. On April 10 2008, UC Berkeley graduate journalism student James Karl Buck and his translator, Mohammed Maree were arrested in Egypt for photographing a local anti-government protest. On his way to the police station, Buck used his mobile phone to twitter the message “Arrested” to his 48 followers who contacted the UC Berkeley, the US Embassy and a number of press organizations on his behalf. While being detained Buck was able to send updates about his condition to his followers. As a result of the message and the efforts of his Twitter friends, he was released the next day from the Mahalla jail after the college hired a lawyer for him.
Research published in New Scientist magazine in May 2008 found that blogs, maps, photo sites and instant messaging systems like Twitter did a better job of getting information out during emergencies such as the shootings at Virginia Tech than either the traditional news media or government emergency services. The study -- done by researchers at the University of Colorado also found that during the fires in California in October 2007, those using Twitter kept their followers, who were often friends and neighbors, informed of their whereabouts and of the location of various fires on a minute by minute basis. Additionally, organizations that support relief efforts are also using Twitter. The American Red Cross uses Twitter to exchange minute-to-minute information about local disasters, including statistics and directions.
The first trade union Twitter service was launched by the news and campaigning website LabourStart in June 2008.