Stimulansbloggen has a good post on 'greenwashing' which seems to be increasignly popular in advertising. It never fails to annoy me to see ads doing the green thing put out by a company or shilling a product that clearly isn't.
The danger of greenwash is that when companies use unsubstantiated green claims, they confuse consumers who want to do the green thing. This confusion might turn into a reason for consumers to do nothing at all. If everything seems green it becomes unreasonably hard to find the "real" green alternative.
Stimulansbloggen also points to the usful greenwash guide put together by ad agency Futerra (and where the image on the left is from).