I've been keeping an eye on social media chatter about laws in some states that would mandate labeling for products containing genetically modified organisms. I'm not a biologist or a food scientist, but my understanding of the scientific consensus is that GMOs aren't harmful (I've been following the University of Florida's Kevin Folta on Twitter for coverage and commentary).
This looks like a situation in which mandatory labeling can make information problems even worse by compounding erroneous beliefs. This looks like a campaign to place warning labels on essentially safe products that capitalizes on the fact that "Genetically Modified Organisms" just sounds scary. While it looks like a public-interest campaign based on an innocuous right to know, I don't think we should be naive about what these initiatives stand to do to the demand for non-GMO products.
Speaking of which, this is an information "problem" the market is already solving. There is a huge market for organic and non-GMO foods, and the infrastructure is already there for labeling and certification of organic/non-GMO foods. At best, mandatory "contains GMOs" labels are superfluous.
At worst, though, they compound erroneous beliefs. Again, "genetically modified organism" elicits visions of mad scientists creating unholy creatures in secret labs and plays to our innate fear of technology. I suspect that most people upon seeing a "contains GMOs" warning label will infer "this must be bad for me." That's a tragedy given that, as I understand it, GMO crops are perfectly safe. In a world where chronic hunger is still a problem, it's especially tragic.