How do you export a premium car brand from Germany? Well, if you're BMW, you might try a catapult, but don't bet on the car maker or its ad agency, GSD&M Idea City, taking credit for the idea.

Rather than slapping together a traditional 30-second spot or opting to deploy a never-ending stream of widgets, BMW chose to tell an unconventional story about a fictional German town bent on catapulting a car to the U.S. However, instead of announcing its involvement in the campaign, BMW let the 30-minute mockumentary and ancillary web elements stand alone.

While the idea of launching an off-kilter marketing campaign designed to look like a real life occurrence is nothing new, such a decision is not without risk. In the past, campaigns that were later discovered to be marketing ploys, like the "Aqua Teen Hunger Force Movie" debacle in Boston, ending up hurting a brand's reputation.

"The most precious thing that a brand has with its target audience is trust," Jim Nail, co-chairman of the ethics committee at the Word of Mouth Marketing Association, told The Wall Street Journal. "If you do some of these things where the clear intent is to deceive -- whether it's through the spokesperson or the facts or the relationship to the company -- then people feel abused."

But so far BMW has found the response to be overwhelmingly positive, perhaps because the campaign was done with a wink and a nod ala "This Is Spinal Tap," the film that pioneered the mockumentary genre.

Scott Brewer, art director for GSD&M, called the idea "tongue-in-cheek" and pointed out that the heart of the campaign was to let people have fun with the experience, whether they believed it to be an ad or a real project.

To help add to the spirit of the story, GSD&M created Facebook profiles for some of the characters featured in the movie and launched a website for the builder of the catapult.