In any case, the thrust of the "pro" side (i.e., GMOs are a growing concern) centers around food safety, and the possibility for cross-contamination of GMOs into non-GM crops. Madill and Illuminato say:
One persistent danger lies in the prospect of crops unapproved for human consumption becoming mixed with the food supply. In 2000, Friends of the Earth and other groups discovered an unapproved strain of genetically modified corn on grocery store shelves. StarLink corn, which had been deemed safe only for animal consumption because of human allergen concerns, was showing up in Kraft (KFT) taco shells. The discovery led to recalls, mill closures, halts in exports, and buybacks of contaminated corn.
On the con side, Greenwood argues that GMOs represent the best chance at feeding the world's ever increasing population:
While there is no easy and singular solution to starvation, we know that biotechnology can expand and enhance the global food supply. Over the past decade agricultural biotechnology has improved plant productivity and crop quality, increased farmer income, supported stewardship of the land, and contributed to a safe food supply. Biotech crops constitute part of the diet of billions of people around the world without one single documented health problem.
Each is certainly a reasonable argument, and lacking any indication of what the long term effects of GMOS might or might not be, it's really hard for me to take a side here. But don't consumers have a right to know whether the product they are buying contains GMOs, thereby leaving the decision up to them as to whether they want to eat the stuff? As of now the U.S. has no law mandating GMO labeling, a fact that leads to even more skepticism and fear in consumers. What are these companies trying to hide?