Advertising once required very little effort on the part of the consumer. You turned on the TV or opened the newspaper and there it was.

But an increasing number of advertisers are calling on consumers to participate in their campaigns by sending in photos of themselves, customizing movie trailers and even playing with a virtual online cat.

It's called interactive advertising, and agencies are embracing it as a way to cut through the clutter even though there's little data on the effectiveness of the approach.

Los Angeles-based New Line Cinema, a unit of Time Warner Inc., attributes part of the success of its current release "Wedding Crashers" to a feature that allows people to insert their own pictures in place of stars Owen Wilson and Vince Vaughn to create a mock trailer. Roughly 100,000 people participated in the campaign, dubbed "Trailer Crashers," and the customized trailers were viewed about 2 million times, according to New Line.

"When a consumer makes the effort to put (his or her picture) in there, they get invested in the product," said Gordon Paddison, executive vice president of integrated marketing for New Line, who acknowledged that "no one yet has been able to determine the valuation of this."

Nevertheless, there's little question that it's been a boon for the ad agencies specializing in the approach. iQ magazine, which covers interactive technology, reported that many of the largest interactive agencies grew 15 to 30 percent in revenues between 2003 and 2004. TEQUILA\ Los Angeles has doubled its billings each year since it was founded in 2002 to more than $100 million last year, according to Kristi Vandenbosch, president of the agency's L.A. office.

The office has grown by turning such well-known brands as Sony Corp.'s PlayStation and Nissan Motor Co. Ltd.'s Xterra into interactive experiences. For the PlayStation game "The Getaway," TEQUILA\ created a virtual online pub (the game is set in London) in which the user inhabits one of the characters from the game and gets to meet the others. The Xterra feature is more typical of automotive Web sites, where the user can scroll among vehicle features and build a customized SUV.

The build-your-car feature is among the more common interactive components of online advertising and, at more than five years old, no longer feels novel.

Rubin Postaer and Associates, a Santa Monica ad agency, took a more offbeat approach to selling cars for its client, American Honda Motor Co. Inc.

Last year, Rubin Postaer created a campaign in which car owners sent in photos of themselves and their cars depicting the similarities between the two. Then, viewers of the site were invited to vote on which car and human most closely resembled each other. The campaign included a television commercial, Web site and direct mail advertisement that was dubbed "Honda love."

"It was purely a brand image commercial," said Pete Imwalle, senior vice president and general manager of Rubin Postaer's interactive division. "It really was designed to help people think of their connections with their cars on an almost personal level."

But do the warm-and-fuzzies help move Accords and Civics? "How do you measure success these days?" Imwalle asked. "It's not just the number of impressions on a Web site. The more senses you touch, the more recall people have."

KVEA-TV (Channel 52), the Telemundo affiliate in L.A., is emphasizing interactivity in lower-tech ways. Viewers were invited to submit photographs of themselves and their families for a campaign emphasizing the station's intimate connections to the people who watch it. Some of the photos, along with ones taken by KVEA staff at events promoting the station, appear on billboards and bus shelters.

The campaign, which launched in May, has elicited more than 200 photographs from viewers, said Ginger Zumaeta, vice president of advertising and promotion for KVEA.

"Once you get personally involved in the station as a viewer, that means you're engaged," Zumaeta said. "We're constantly looking for ways to engage our audience."

The popularity of interactive advertising owes in part to the emergence of a new generation schooled on joy sticks and the Internet and who expect to control what's on the screen. It's also being driven by advertisers seeking new ways to get noticed in an ad-saturated world, said Gerard Tellis, a professor of marketing at USC's Marshall School of Business.

"The noise level of ads is very high," Tellis said. "Because of the high noise level and the busy consumer, marketers are looking for any way to break through."

Mars Inc., whose Masterfoods USA unit manufactures Whiskas cat food, incorporates an interactive cat into the Whiskas Web site. The cat was developed by the Los Angeles office of TEQUILA\, the interactive division of Omnicom Group Inc.'s TBWA\Chiat\Day.

The online cat mimics the behavior of a real feline, even responding when a user moves a cursor over it. The online cat isn't merely for amusement, however. It scratches a bag of dry Whiskas and eventually leads the user to a $2 off coupon that the user can print out.

"He's doing his job from both an entertainment standpoint and as a little marketing tool," said Vandenbosch. "If we can deliver a message in an interactive environment, we deliver a much more robust experience for the consumer, which helps lead to a purchase decision."

There's a danger that if too many brands attempt interactive campaigns for the sake of doing so, the approach could become gimmicky. Paddison, who helped create "Trailer Crashers" for New Line Cinema, said any company considering an interactive campaign must always be guided by the bottom line: getting a sales response from consumers.

"As soon as you say this is the Holy Grail, it becomes an end in and of itself as opposed to a means to go out and promote a product," he said.

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