Hackers broke into the Twitter feeds of Fox News and PayPal this week, raising concerns about how secure the microblogging site is as it increasingly becomes a platform for news dissemination.

Twitter, which allows people to send 140-character text messages, or Tweets, to groups of so-called followers, is one of the most popular social networking services on the Web, along with Facebook.

Here are five prominent news events that broke on Twitter:

OSAMA BIN LADEN'S DEATH

In the time between the White House announcing a late-night press conference, and President Obama telling the world Osama bin Laden had been killed, one Twitter user had already broken the news of his death on May 2.

Keith Urbahn, the chief of staff for former defense secretary Donald Rumsfeld, wrote, So I'm told by a reputable person they have killed Osama Bin Laden. Hot damn.

Urbahn later said he did not know for certain if Bin Laden was dead, but that the bar for checking sources is much lower in Twitter.

HUDSON RIVER PLANE CRASH

When US Airways flight 1549 unexpectedly landed in the Hudson River in New York City in January 2009, Twitter users were among the first to break the news and post photographs.

Janis Krums tweeted a picture of passengers on the wings of the floating Airbus passenger jet: There's a plane in the Hudson. I'm on the ferry going to pick up the people. Crazy.

The incident is an example of how Twitter and other social media sites allow anyone with a smartphone to break news.

ROYAL WEDDING ANNOUNCEMENT

The Clarence House Twitter feed had all the details on Prince William and Kate Middleton's wedding in Britain.

The Twitter feed for the Prince of Wales announced in early January detailed plans for the big day, including the date of the wedding, how the bride would arrive, and who would conduct the royal ceremony.

Twitter has been well received among celebrities such as Charlie Sheen, who used the platform to rail against his employer CBS on his way to more than 4 million followers.

U.S. PRESIDENTIAL CAMPAIGNS

U.S. presidential candidates on both sides of the aisle used Twitter to announce their 2012 election campaigns.

Newt Gingrich wrote, Today I am announcing my candidacy for President of the United States. He also Tweeted a link to a video of his announcement.

Obama announced his 2012 campaign in a social media blitz on April 4. On July 6, the president held a Twitter townhall where he pressed his economic agenda and poked fun at Republicans. Obama, who is not known for brevity, tweeted, One last point -- I know Twitter, I'm supposed to be short.

HILLARY CLINTON WON'T WORK TWICE UNDER OBAMA

CNN issued a tease on Twitter about an interview with Secretary of State Hillary Clinton in which she said she would not stay on President Obama's cabinet if he is elected to a second term.

A CNN executive producer tweeted on March 16 that Hillary Clinton would NOT be in an Obama 2nd term cabinet.

The Tweet was an advertisement for a later interview on CNN with Clinton, and highlighted one way news companies use the social media tool.

Sources: Reuters, other news reports

(Reporting by Roy Strom; Editing by Richard Chang)

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