Sydney-based Ecocho founder Tim Macdonald had an idea; build a search engine based on Google and Yahoo technology and use the ad revenue to plant two trees for every 1,000 searches, offsetting tons of carbon dioxide. However, the practice of "compensating users for viewing ads or performing searches, or promise compensation to a third party for such behavior" is a violation of Google AdSense policy and Google decided to pull support of the site, on Earth Day no less. Macdonald claims Google is not enforcing its rules to other "green" search engines such as Blackle, though Blackle is not making the same claims.