As Hurricane Sandy pounded the U.S. Atlantic coast on Monday night, knocking out electricity and Internet connections, millions of residents turned to Twitter as a part-newswire, part-911 hotline that hummed through the night even as some websites failed and swathes of Manhattan fell dark.
But the social network also became a fertile ground for pranksters who seized the moment to disseminate rumors and Photoshopped images, including a false tweet Monday night that the trading floor at the New York Stock Exchange was submerged under several feet of water.
The exchange issued a denial, but not before the tweet was circulated by countless users and reported on-air by CNN, illustrating how Twitter had become the essential - but deeply fallible - spine of information coursing through real-time, major media events.
But a year after Twitter gained attention for its role in the rescue efforts in tsunami-stricken Japan, the network seemed to solidify its mainstream foothold as government agencies, news outlets and residents in need turned to it at the most critical hour.
Beginning late Sunday, government agencies and officials, from New York Governor Andrew Cuomo(@NYGovCuomo) to the Federal Emergency Management Agency (@FEMA) to @NotifyNYC, an account handled by New York City's emergency management officials, issued evacuation orders and updates.
As the storm battered New York Monday night, residents encountering clogged 9-1-1 dispatch lines flooded the Fire Department's @fdny Twitter account with appeals for information and help for trapped relatives and friends.
One elderly resident needed rescue in a building in Manhattan Beach. Another user sent @fdny an Instagram photo of four insulin shots that she needed refrigerated immediately. Yet another sought a portable generator for a friend on a ventilator living downtown.
Emily Rahimi, who manages the @fdny account by herself, according to a department spokesman, coolly fielded dozens of requests, while answering questions about whether to call 311, New York's non-emergency help line, or Consolidated Edison.
At the Red Cross of America's Washington D.C. headquarters, in a small room called the Digital Operations Center, six wall-mounted monitors display a stream of updates from Twitter and Facebook and a visual "heat map" of where posts seeking help are coming from.
The heat map informed how the Red Cross's aid workers deployed their resources, said Wendy Harman, the Red Cross director of social strategy.
The Red Cross was also using Radian6, a social media monitoring tool sold by Salesforce.com, to spot people seeking help and answer their questions.
"We found out we can carry out the mission of the Red Cross from the social Web," said Harman, who hosted a brief visit from President Barack Obama on Tuesday.