If you launch a campaign designed to push somebody to do something, the simpler and more tangible that action is, the greater the odds that they’ll comply.

I had thought this was something Greenpeace grasped based on the success of their campaigns targeting Nestle and Mattel. (I wrote about the Mattel campaign on Monday.) From Nestle, they wanted the company to stop buying palm oil that was obtained by its supplier from the rainforest where the habitat of the orangu-tan was threatened. Mattel switched suppliers—and developed a new, green procurement policy—to buy packaging materials that don’t come from companies using objectionable logging practices.

Now, however, Greenpeace has launched a campaign against Volkswagen that uses many of the same elements. But in this case, the objectives are broad and certainly not as actionable as changing one thing.

The tactics included taking over some UK billboard advertising and launching a YouTube video. They’re also leveraging cultural references, this time the Darth Vader TV commercial Volkswagen ran during the Super Bowl (it went viral on YouTube, having been viewed more than 40 million times).

Unlike the Mattel campaign, which was housed on Facebook where individuals posting to the wall helped spread the word through news feeds, the VW campaign is on a microsite where you have to enter personal information in order to lend your support to the campaign.

But the biggest problem with the campaign is its goals. There are three: support strong C02 emission cuts, support strong fuel efficiency standards, and “put your technology where your mouth is.”

I’m not about to pass judgment on whether these are achievable or noble; you’ll have to visit a green blog for that kind of analysis. But Greenpeace has been able to point to real successes when Mattel and Nestle caved in to pressure and changed suppliers. The overarching goals of the VW campaign, on the other hand,  can’t be achieved in the span of a campaign. Even if VW decided to comply, it would require re-engineering, retooling and other significant business process changes that can’t happen overnight in a company that size. The first new car to adopt lower emission standards wouldn’t hit showroom floors for at least three years.

Getting VW to take these actions is consistent with Greenpeace’s mission, but there are other approaches to take for these longer-term objectives than the short-term impact of one of these cultural-reference campaigns.

There’s a lesson here for communicators and marketers. The easier it is to do what you’re asking someone to do, the more likely it is that they’ll do it.