I watched the documentary The Future of Food tonight. It is a really good DVD and I recommend it to everyone that is interested in what they are eating. It is about GM food. It is truly terrifying when you think about it. They've changed the genes of plants and these genes have ended up in other plants. The wild corn in Mexico now have the roundup ready gene in it even though they banned the planting of GM corn in Mexico. It is bad enough that the seeds end up escaping and growing in the wrong fields but the fact that the genes are actually ending up in other plants is horrible. Especially because they now have crops with the terminator gene in them, which is a gene that keeps the plant from making seed and growing for another generation. Imagine if this gene ended up in other plants? It could easily become the case that all corn in this country would be unable to make seed (this could happen in any plant, even non-crop plants). I have a PhD in biotechnology related stuff and I know how easy it is for genes to enter other organisms.
I really see the potential for our whole food supply to become contaminated. I don't think people realize how much of our food supply is already GM. Pretty much anything with corn syrup or soy lectithin is GM. There is also a real possibility of the added genes recombining with our own DNA including the antibiotic resistance gene that is included in every GM crop for easy selection of the modified seed.
It is also believed that the pollen from the Bt corn (which is GM corn that contains the gene for an insecticide) might be causing the problems in the honeybee populations.
Here is a good place to read more about GM foods: http://www.organicconsumers.org/gelink.cfm
Here is a campaign against Monsanto, the producer of pretty much all the GM seed: http://www.organicconsumers.org/monlink.cfm