Audiences are voicing snap judgments on movies faster and to more people than ever before on Twitter, and their ability to create a box office hit or a flop is forcing major studios to revamp marketing campaigns.

The stakes are especially high this summer season when big budget movies like Harry Potter and the Half-Blood Prince, which opened on Wednesday, play to a core audience of young, plugged-in moviegoers.

Box office watchers say Twitter, a micro-blogging service that allows anyone to post on-the-fly wisecracks for all the world to see, is the latest weapon in an arsenal of cell phones and computers that audiences use to critique films quickly, often when they are still sitting in theaters.

Such word-of-mouth publicity from fan to fan can boost, or bomb, ticket sales.

Has everything speeded up? The answer is yes, said Adam Fogelson, Universal's president of marketing and distribution. Depending on how big your opening day audience is, word-of-mouth starts playing a factor immediately, he said.

Film marketers look at weekly declines in ticket sales to judge fan buzz. In recent years those drops have widened significantly as communication has speeded up thanks to the Internet and more recently social networking services like Twitter and Facebook.

This summer, which is the most lucrative movie season and can make up as much as 40 percent of annual box office, ticket revenues for new films have dropped 51 percent, on average, from week No. 1 to week No. 2, a figure matched only in 2007, according to tracking firm Box Office Mojo.

If people don't like the movie now on Friday it can die by Saturday, said Paul Dergarabedian, president of tracking firm Hollywood.com Box Office.

BRUNO GETS TWITTERED

Last Friday, actor Sacha Baron Cohen's gay-themed comedy Bruno, which was distributed by Universal Pictures, made an impressive one-day debut of $14.4 million at U.S. and Canadian box offices, but the next day it suffered a large single-day drop, falling 39 percent to $8.8 million.

Media reports speculated that Bruno suffered from the Twitter effect, meaning audiences reacted quickly online to raunchy scenes of sex and nudity, scaring people away.

Soon after the movie's opening, Twitter was awash with comments such as this from user Cathy Zhang: Some scenes from Bruno I'll never erase from my mind. On the flip side, many Twitter commentators raved about Bruno.

Universal's Fogelson said even Twitter comments that seem critical can be good publicity because they show people are passionate about the movie and can spark discussion that increases attendance. He attributed Bruno's lopsided opening day not to negative fan buzz, but to an unusually large crowd of Cohen's fans rushing to see the film on its first day.

Hollywood has a long history of both embracing and spurning new technology. In the case of Twitter, it is giving an early embrace. Sony Pictures, for instance, has been notably aggressive, creating Twitter pages for upcoming movies District 9, Julie & Julia and The Ugly Truth.

Using Twitter, actor Ashton Kutcher has raised his profile and that of his production company among the most tech-savvy, and he is not alone. Filmmakers and actors often tweet from the set with the blessing of publicists looking to create interest in a film.

As much as it seems chaotic, it's not. It's just extremely quick and real-time, said online marketing consultant Gordon Paddison.

(Editing by Bob Tourtellotte)

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