Usage of Twitter

On April 10, 2008, James Buck, a graduate journalism student at University of California, Berkeley, and his translator, Mohammed Maree, were arrested in Egypt for photographing an anti-government protest. On his way to the police station Buck used his mobile phone to send the message “Arrested” to his 48 "followers" on Twitter. Those followers contacted U.C. Berkeley, the U.S. Embassy in Cairo, and a number of press organizations on his behalf. Buck was able to send updates about his condition to his "followers" while being detained. He was released the next day from the Mahalla jail after the college hired a lawyer for him.

Research reported in New Scientist 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, performed by researchers at the University of Colorado, also found that those using Twitter during the fires in California in October 2007 kept their followers (who were often friends and neighbors) informed of their whereabouts and of the location of various fires minute by minute. 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.

Media outlets use Twitter as a source of public sentiment on issues. The first trades union Twitter service was launched by the news and campaigning website LabourStart in June 2008[64] During the CBC News television coverage of the Canadian federal election on October 14, 2008, the CBC cited a graph, produced by the Infoscape Research Lab, of items mentioned on Twitter, along with Tweets regarding Elizabeth May and Stéphane Dion, with the majority of the Dion Tweets calling for him to step down in response to the election results.

In October 2008, a draft US Army intelligence report identified the popular micro-blogging service as a potential terrorist tool. The report said, "Twitter is already used by some members to post and/or support extremist ideologies and perspectives."

During the 2008 Mumbai attacks, eyewitnesses sent an estimated 80 tweets every five seconds as the tragedy unfolded. Twitter users on the ground helped in compiling a list of the dead and injured. In addition, users sent out vital information such as emergency phone numbers and the location of hospitals that needed blood donations.[68] In January 2009, US Airways Flight 1549 experienced multiple bird strikes and had to be ditched in the Hudson River after takeoff from LaGuardia Airport in New York City. Janis Krums, a passenger on one of the ferries that rushed to help, took a picture of the downed plane as passengers were still evacuating and sent it to Twitpic before traditional media arrived at the scene. In February 2009, the Australian Country Fire Authority used Twitter to send out regular alerts and updates regarding the 2009 Victorian bushfires. During this time the Prime Minister of Australia, Kevin Rudd, also used his Twitter account to send out information on the fires, how to donate money and blood, and where to seek emergency help.

The first criminal prosecution arising from Twitter posts began in April 2009 in Oklahoma City, Oklahoma. Agents of the Federal Bureau of Investigation arrested Daniel Knight Hayden, a supporter of the Tea Party protests against the policies of President Barack Obama. Hayden was allegedly sending tweets threatening violence in connection with his plan to attend the Tea Party protest in Oklahoma City. In May 2009, astronaut Michael J. Massimino used Twitter to keep updates of their Hubble Space Telescope repair mission, marking the first time Twitter was used in space.
On February 12, 2009, Twitter was used to organise a global meet-up called Twestival where Twitter users came together in over 170 cities worldwide in the first meeting of purely Twitter users. The event was used to raise awareness and money for Charity: water.