PS: My sister created GMO's for a while in her words the process is way less controlled than generally portrayed.
Both the processes and the regulatory compliance requirements around GMOs provide a lot stronger (though, still, not perfect) assurance of that for GMOs than the processes and (near complete lack of) regulatory clearance requirements around crop modifications that result in rapid genome changes but which are considered "traditional breeding" rather than "GMO" because they don't involve directly inserting genetic material from a different organism.
(I have an immediate family member who works doing both kinds of crop modifications, and has been involved providing science support for regulatory clearance of products, as well.)
http://en.wikipedia.org/wiki/Organophosphate
Unlike normal mutations genetic modifications can change a lot of things at the same time and are often focused around biologically active chemicals. That's not to say that GMO foods are unsafe just that new modification are far from risk free and should have stringent review before using them to feed 100+ million people. If for no other reason than they can produce a lot of a completely unknown and unresearched chemical.
Consider a recent (1992) example that has nothing to do with DNA modification. Hedysarum alpinum is now known to be toxic, but was not noted to be so in a field guide which may have contributed to Christopher McCandless death. http://en.wikipedia.org/wiki/Christopher_McCandless EXTREMELY WEAK. FAULT OF POT[ATO] SEED. MUCH TROUBLE JUST TO STAND UP. STARVING. GREAT JEOPARDY.
> If for no other reason than they can produce a lot of a completely unknown and unresearched chemical.
I don't think this is true. Metabolic engineering is really hard. In other words, getting an organism to produce a new small molecule is really hard. If it weren't, we would have large scale biosynthesis of lots of stuff, instead of relying on chemical synthesis or isolation. Most enzymes have very specific functions. E.g. an enzyme will add a carbon at a particular location on a very specific substrate molecule. There's not really the possibility for unforeseen byproducts.
What you describe isn't really plausible, which is why biologists agree GMOs are safe. A plausible hypothetical for how something bad could happen, and then not be noticed until the product is fed to millions of people, probably doesn't exist (based on the fact that one has yet to be proposed).
The only exception I know is allergenicity, but this is a general risk. People are allergic to stuff. Any new product is potentially allergenic. All of a sudden quinoa is in vogue.... people could be allergic to quinoa. No unique risk.
The toxicity of _Hedysarum alpinum_ is an evolved trait, like most toxicities, that confers some benefit to the host organism. It's hard to accidentally create a beneficial new trait in organisms. It's even an academic problem in the field--evolution of novelty. Most genetic changes you make either break stuff or if you're lucky do one specific thing.
A large part of why this is hard is they tend to produce something other than what you want. Getting a protean to fold the right way 95% of the time is a huge achievement, but it also means your producing something else 5% of the time. In point of fact quite a bit of your DNA is focused on getting other sections to fold correctly.
As to population risks Prion's are probably a risk. http://en.wikipedia.org/wiki/Prion For one thing there unlikely to be undetected in the food supply as normal toxicity tests will miss a novel one. (EX: Mad Cow Disease)
Anyway, all I am really just suggesting GMO’s are introduced more slowly. Something like food for 100k people in the first year, 1M the next, then 10M and then you’re good to go. Granted, that would be really hard to do with the way the current food supply works, but simple acreage limits could have a similar effect.
PS: The point about Hedysarum alpinum toxicity was it's not all that uncommon and people had been eating it, but it was not known to be toxic. The point being Toxicity can be more complex issue than is generally assumed.
Food shortage is a real problem that affects a billion people.
We should weigh potential risks against this.
Just the difference between people in the US eating beef and chicken costs aproximately enough to feed the entire US population a subsistance diet.