This is how it works. A major motion picture studio has to promote its new project in time for opening weekend. So it constructs prop replica automobiles inspired by the film and plants them around the city. Passers-by take photographs and send phone-pix to their friends, who in turn tell their friends about the movie tie-in. Bloggers also do their part and gather material for their website, taking pictures of the aforementioned car and blasting it to their audience. And as a result, you read about it and convince yourself that you want to go watch The Green Hornet this weekend. Great success.