The MoonPublicity.com business model is best summarised by this paragraph on one of the pages of their website:
"Let’s suppose it would cost a billion dollars to create and send a fleet of Shadow Shaping robots to the moon, the project would pay for itself in less than 3 years after completion. Over the next 50 years it would generate 18 billion dollars worth of advertising. And since there is no atmosphere on the Moon, the image could last for thousands of years."
I'm not sure how they will deal with all the craters, not to mention the lunar conservationists!
See also the interesting comments on the Gizmodo article about this project.