NEW YORK — Cassy Hayes and Jasmine Coleman were among the first fans to arrive outside the Ronald Reagan UCLA Medical Center in Los Angeles where Michael Jackson was brought and later pronounced dead.

How had Hayes, 25, and Coleman, 21, heard the news so quickly?

Twitter.

The two young women had learned about Jackson's health like so many who get their news nowadays: by reading the ever-flowing feed of real-time information on the microblogging service.

Jackson's unexpected death at 50 was just the latest major news event where Twitter played a central role. But just as quickly as Twitter has emerged as a news source, so, too, has its susceptibility to false rumors become abundantly apparent.

The extraordinary amount of news coverage the mainstream media has recently devoted to Twitter has led some to think the press is in love with the 3-year-old microblogging service. But it's a jealous love.

Twitter's constantly updating record of up-to-the-minute reaction has in some instances threatened to usurp media coverage of breaking news. It has also helped many celebrities, athletes and politicians bypass the media to get their message directly to their audience.

Make no mistake about it, Twitter has in many ways been a boon to the media. It's one more way a story might go viral and it's arguably the best way for a news outlet to get closer to its readership. Most outlets now have a presence on Twitter with a feed directing readers to their respective sites.

But even in an Internet world that has for years eroded the distance between media and consumer, Twitter is a jolt of democratization to journalism.

To date, the most salient, powerful example of Twitter's influence has been Iranian protesters using the service (among other methods) to assemble marches against what they feel has been an unjust election.

Early in the protests, the State Department even urged Twitter to put off maintenance that would have temporarily cut off service. Twitter is difficult for governments to block because tweets — 140 characters or less — can be uploaded from mobile phones like a text message. (The Iranian government has nevertheless often succeeded in blocking Twitter, Facebook and other social networks.)

Further, many Americans were upset at what they considered CNN's thin early coverage of the revolution in Iran and voiced their complaints (where else?) on Twitter. Some said they preferred news on Twitter to the cable news network.

Twitter also produced eyewitness accounts of the Mumbai terrorist attacks last year. And when the US Airways jetliner crashed into New York's Hudson River, Twitter was among the first places photos of the landing were linked.

Many users have become accustomed to clicking on Twitter when news breaks. There, they can find a sea of reaction, commentary and links to actual articles.

The popular technology blog TechCrunch recently questioned whether Twitter is "the CNN of the new media generation."

"Twitter absolutely changes the media landscape," said Ross Dawson, author and communications strategy analyst. "I like to refer to Marshall McLuhan's description of media as 'an extension of our senses.' Now, Twitter is extending our senses to tens of millions of people who are often right on the scene where things are happening."

Ashton Kutcher, one of Twitter's most popular users, in an earlier Web video evoked the rhetoric of a revolutionary: "We can and will create our media." Kutcher, who declined an interview request, sees Twitter as putting media power in the hands of regular people.

But comedian Michael Ian Black, a popular figure on Twitter, notes that while Twitter allows someone to "communicate very directly with people," it also allows you to keep them "totally at arm's length."

There are no follow-up questions on Twitter if the user chooses not to hear them. When tweets replace an interview or a press conference, something is lost. Twitter can thus be used to control one's message and one's image.

Cyclist Lance Armstrong, for example, has caused some news organizations to question how they approach Twitter. Armstrong often treats Twitter as his primary news outlet; in May, during the Tour of Italy, his end-around of the media caused some news organizations to boycott his tweets.