Although word of mouth could always make or break a movie, it usually took days to affect the box office. But the rise of social networking tools such as Twitter might be narrowing that time frame to hours. And that has Hollywood on edge.
This summer, movies such as Brüno and G.I. Joe have had unexpected tumbles at the box office - just within their opening weekends - while Transformers: Revenge of the Fallen survived blistering critical reaction to become a blockbuster.
Box-office watchers say the dramatic swings might be caused by Twitter and other social networking sites that can blast instant raves - or pans - to hundreds of people minutes after the credits roll.
"Almost every time after I go out [to a movie], I'll tweet about it," says Lindsay Wailes, a cook and barista from Westminster, Md. "I tweeted about G.I. Joe as soon as I left the theater."
Her take: "If you like science or plot, this isn't a movie for you; if you like explosions for no reason, you'll love it."
She also listens to what others have to say: She turned her back on Brüno because of downbeat Twitter reviews. Studios are trying to gauge the impact of an avalanche of tweets and how it affects the staying power of a movie. Was the 39 percent box-office drop of Brüno from Friday to Saturday a case of disappointed moviegoers tweeting from theater lobbies? Or did a limited fan base for Brüno exhaust itself on that first day?
"I think Twitter can't be stopped," says Stephen Bruno, the Weinstein Co.'s senior director of marketing. "Now you have to see it as an addition to the campaign of any movie. People want real-time news, and suddenly a studio can give it to them in a first-person way."
Eamonn Bowles, president of Magnolia Pictures, says studios are worrying about a time when "people will be Twittering during the opening credits - and leaving when they don't like them." But he also warns, "the next step [for the Twitter Effect] is for studio marketing to manipulate it."
The Weinstein Co. did that big-time for the release of the Quentin Tarantino-Brad Pitt World War II epic Inglourious Basterds.
The company packed a screening at San Diego's Comic-Con with people who won access via Twitter. It also staged "the first ever Red Carpet Twitter meet-up" during the movie's premiere at Grauman's Chinese Theatre in Hollywood, generating celebrity tweets including Sarah Silverman's "just made me smile forever" and Tony Hawk's "another Tarantino classic."
Twitter has broadened the reach of bloggers and other aspiring opinionmakers.
"Just two years ago, if I saw a movie I loved or I hated, I'd be able to tell a dozen friends, tops," says John Singh, who works for the movie and social networking Web site Flixster. "Now I can be walking out of a theater as the credits are rolling and immediately tell 500 people what I thought. . . . It's never been this easy to be this influential."
Take The Proposal, a film that had little buzz yet has become one of the summer's most profitable productions. (It cost $40 million and is grossing upward of $159 million.) Flixster, which runs the Movies application for iPhones, worked with Disney/Touchstone to promote the Sandra Bullock-Ryan Reynolds romantic farce. Singh credits the campaign with increasing the film's opening-weekend haul by 30 percent.
Positive reviews from her Twitter friends can persuade Wailes to attend a film if she's "undecided." If it "gets raves from people I network with, since I know I have something in common with these people, I figure there must be something in the movie that I might want to see."
Gregg Kilday, film editor of the Hollywood Reporter, notes that it's impossible to separate the factors that would explain a film's drop or rise in box office.
"Even if you don't have Twitter, a lot of people, especially kids, have long had the ability to text each other, sometimes from within the theater," he says. "And for a lot of the mass-market movies, the potential audience will go whether friends tell them they're good or not."
Brandon Gray, president and founder of boxofficemojo.com, notes that the hit teen-romance vampire film Twilight dropped 41 percent from Friday to Saturday without any discussion of the Twitter Effect.
"There have been many indications through the years that films targeting teens and young adults will have a huge Friday and a more front-loaded weekend," Gray says. "That's just kind of how it goes."
Movietickets.com recently ran a poll in which 88 percent of the voting sample said Twitter had no effect on them. Joel Cohen, the company's executive vice president and general manager, thinks "we may be putting too much weight onto the Twitter Effect. But you can see Twitter's benefits as a communications tool that spreads the word about a film, and the negatives have yet to be proven."
Bowles, who distributed the documentary Food, Inc., acknowledges that "we did some Twitter-specific things, including a Twitter-cast with the movie's director, Robby Kenner."
But he's cautious when it comes to describing Twitter as a "revolutionary" force.