LOS ANGELES (Reuters) - Hollywood is increasingly relying on Twitter and Facebook to gauge popular buzz on movies even before they come out, in a move reflecting the power of average filmgoers over once-mighty film critics and detailed surveys.

Studio executives are finding it's important to track the instant reactions of ordinary people to their new offerings, and companies are springing up to provide tools that both monitor and analyze buzz on social networking sites.

In other words, buzz is the amount of chatter or interest in a movie, which can increase awareness of the film and help drive box office sales.

In the past, movie studios relied heavily on focus groups, audience surveys and reviews by film critics to anticipate how their films would fare at the box office.

But recent months have underscored the influence of online word-of-mouth in a world where a Twitter comment can help break or make a movie.

"The writing is on the wall much quicker than ever before," said Pete Blackshaw, executive vice president of Nielsen Online's digital strategic services, which is one of the largest such services working with studios.

"If you know the dog's not going to hunt, at what point do you start to get more efficient and say, 'OK, we're not going to spend everything, maybe we save the marketing budget for DVD,'" Blackshaw said.

Online buzz drove "Paranormal Activity" to a $7.9 million box office in the U.S. and Canada last weekend, setting a record for a movie playing in less than 200 theaters. The low budget horror flick is now on its way to wider release.

INSPIRED BY BRUNO
But in July, the raunchy comedy "Bruno" gave a lesson in the perils of another kind of audience horror, as it suffered a sharper than usual box office drop after its opening following negative comments by individuals on websites like Twitter and Facebook.

But all was not lost. "Bruno," which made a disappointing $60 million at U.S. and Canada box offices, inspired a new service to measure online reaction to movies.

A creation of advertising firm Bradley and Montgomery, the outfit Fizziology puts out a weekly chart showing which movies are getting people talking.

Two days before the Paramount Pictures release "Paranormal Activity" opened in 160 movie theaters, the Fizziology web chart showed it was generating more online buzz than such highly anticipated films as November's "Twilight" sequel "New Moon," and that people were saying good things.

"What's really cool about this is the fact that we're listening in and we're paying attention, and folks don't even necessarily know," said Ben Carlson, co-creator of Fizziology.

"When someone comes out of 'Paranormal Activity' and says, 'It was so scary I won't sleep again,' that's positive buzz."

Christine Birch, president of marketing at DreamWorks Studios, said marketers are increasingly taking into account what average moviegoers say online.

"It used to be way back in the stone age of 2004 that the digital person would simply say, 'We've got lots of online buzz,' and you just never knew what that meant," she said.

"And I think there are a lot of tools being developed to add structure and accountability to that discussion."

In a study, media research firm Interpret found 74 percent of Twitter users have seen a movie in the theater in the past six months, compared to 60 percent of the general population.

Movie marketing firm Stradella Road found that 73 percent of moviegoers have profiles on a social networking site.

Mark Ghuneim, founder of tracking firm Trendrr, said "the live Web has now hit a critical mass."

"You can't go into a movie theater without seeing the wonderful glow of a cell phone or a Blackberry," he said.