I was cruising the bookstore today and found the December 7th copy of The Economist magazine. One of the notes on the cover was about how "ethical food" purchases was actually a negative for the world. I can't get you a link to an online version but the NY Times offers a review of a different Economist article of the same premise.
One point I read in the bookstore that I found relevant was the aspect of paying more for fair trade products thinking you're doing something good that may not actually generate the extensive benefits you had hoped for. It's like the blue box program. Throw in your glass jars and you're doing your part without much effort. The effectiveness of what is being done is overlooked as are the real behavior changes needed to minimize environmental impacts.
I also found it important to note that while changes in consumer behavior can be positive it should not substitute being involved in the political process and forcing structural changes. The article I read specifically discussed agricultural subsidies that harm free trade in goods causing hardship for poor farmers around the world and the implementation of a carbon tax so that the energy used to get us our goods is priced in to what we buy.
You may think The Economist is off the mark but debate is important to generate real solutions. I also feel it is more important to be engaged and be proactive in making changes.