These ads are fun, eye-catching, and are part of Guerilla Marketing techniques. In Marketing Terms' (http://www.marketingterms.com/) these ads are "unconventional marketing methods intended to get maximum results for minimal resources." It's expected that the ads will spark so much interest that people won't be able to stop talking about it, which therefore spreads through word of mouth. I think this tactic is very effective and transforms advertising into something much more because of its interaction with the environment. It almost becomes like a novelty or memorabilia, something to keep record of.