Advertising capital is very precious. Film studios want to ensure that they're getting the best bang for their shareholders' buck, so they are constantly evaluating the merit of each medium, whether it's TV, print, or cyberspace.

Of course, a great idea and superb execution are crucial to the success of any new film. No matter how great those ingredients are, however, they'll still mean nothing unless an equally superb marketing machine backs them. And recognizing the interactive power of the Internet and its growing "clip culture," movie marketers are starting to leverage the Web to make the case for the plot lines under their care.

Movie trailers are nothing but clips, of course, so they fit right into a medium where Google's (NASDAQ:GOOG) YouTube and News Corp.'s (NYSE:NWS) MySpace have done more to shorten the attention spans of the youth than MTV did in its early heyday. Trailers also can be easily searched for and retrieved, which means users can have access to them whenever they want.

In addition, the social networking of destinations such as MySpace is being used to create an aura of excitement around film projects. Time Warner's (NYSE:TWX) Snakes on a Plane got a lot of online buzz before its release, for example. A recent Associated Press article talked about the importance of the Internet to the movie industry and singled out Snakes, since the Web campaign behind the Samuel L. Jackson film is in the running for one of the Key Art Awards, an event that celebrates advertising initiatives.

Besides Snakes, the more recent Borat also benefited from a clever Web machine. But my favorite online buzz-builder of all time has to be The Blair Witch Project. Many people ended up hating that film -- I thought it was brilliant, and I am still a little creeped out by that wacky creature in the woods -- but its website helped to make sure that a ton of moviegoers wanted to pay for the privilege to decide for themselves whether the shaky video lived up to the hype.

There is a risk, though, to buzz-building campaigns: As Web surfers become increasingly jaded, such viral mechanisms might start to appear lame. If the Blair Witch franchise ever sees another entry -- and I shudder at that thought, considering that I unfortunately saw the less worthy sequel -- it might not be so easy to re-create that special vibe that infected the targeted mindshare. That will create challenges for this aspect of Web promotions.

Still, portals such as AOL and Yahoo! (NASDAQ:YHOO) are valued for the eyeballs they deliver. The groups that love to head to the multiplex on a weekend night tend to live on the Net (as well as cell phones), so mediums other than print and TV are looking interesting to those who control the ad budgets. Disney (NYSE:DIS), Viacom (NYSE:VIA), Sony (NYSE:SNE), and all the rest will be counting on websites to persuade people to see their summer blockbusters, hoping that they can create the right balance between banner advertising and social networking to build an equity of awareness.

It's going to be a hot summer at the box office, and Internet businesses will be looking to capture as much as they can of the $3.5 billion that's expected to be spent on movie promoting. Which campaign will achieve the best return on its investment? Stay tuned.

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Fool contributor Steven Mallas owns shares of Disney. As of this writing, he was ranked 4,846 out of 28,939 rated investors in Motley Fool CAPS. Don't know what CAPS is? Check it out. The Fool has a disclosure policy.