In the new issue of BusinessWeek: “Another Inconvenient Truth?” It warns:

Done carefully, offsets can have a positive effect and raise ecological awareness. But a close look at several transactions — including those involving the Oscar presenters, Vail Resorts, and the Seattle power company — reveals that some deals amount to little more than feel-good hype. When traced to their source, these dubious offsets often encourage climate protection that would have happened regardless of the buying and selling of paper certificates. One danger of largely symbolic deals is that they may divert attention and resources from more expensive and effective measures.