I was thinking about this the other day, a couple things that came to mind were -
Is it not due to genetic diversity that we see the great complexity of species that have evolved on this planet, and the resiliency of the biosphere?

It would seem that the introduction of species that are in many ways genetically identical would lead to similar problems that are found in the monoculture crop production of industrial farming, i.e. greater susceptibility to pests and disease.

I also get the feeling that potential risks are not properly accounted for in the current system where wealth is often seen as arbitrary fiat capital and not as the health of our environment, the real wealth as it allows human beings to flourish and fuels the wealth of our ideas and actions.

Say there were detrimental effects of gmo food consumption how long would it take the public to become informed? There is still widespread use of plastics and chemicals with documented scientifically evidenced deleterious health effects. I suspect more people are 'marketed to' than read scientific reports.

There are the classic 'case study accomplishments' of gmo like the modified rice that provided vitamin A to a malnourished population. Counterpoint to this is that we live on an abundantly productive planet and the obstacles to proper nourishment of the members of our species are typically political.

We don't see large percentages of other species that are under-nourished, we also don't see other species that have developed lopsided and convoluted systems as ours have.

Regarding Monsanto et al. -

" Big Biotech with Monsanto leading the pack wants to replace those millions of years with seeds like the Terminator (named for the action hero governor of California) which goes sterile after one growing cycle and obligates farmers (they sign binding contracts with Monsanto) to buy more, a process Mexican investigator Silvia Ribiero tags "bio-slavery". "
- http://www.counterpunch.org/ross02142007.html

" Farmers are forced to sign contracts, agreeing to buy GMO seed at a company-fixed price. Monsanto's super-duper "Terminator" seed, named after California's action hero governor, goes sterile after one growing cycle and the campesinos are obligated to buy more. By getting hooked on Monsanto, Mexican farmers, once seed savers and repositories themselves of the knowledge of their inner workings, become consumers of seed, an arrangement that augurs poorly for the survival of Mexico's many native corns. "

If the number of corn species declines what happens if something like Panama disease that affects bananas were to strike corn crops? Ever more genetic modification, beholden to just a few large corporations for the solution?

A cynic might point out a certain degree of environmental havoc might work to the benefit of gmo companies as far as the short-sighted goals of a fiat currency profit are concerned.

" Moreover, as farmers from other climes who have resisted Monsanto and refused to buy into the GMO blitz, have learned only too traumatically, pollen blowing off contaminated fields will spread to non-GMO crops. Even more egregiously, Monsanto will then send "inspectors" (often off-duty cops) to your farm and detect their patented strains in your fields and charge you with stealing the corporation's property. "

" Mexican corn is, of course, not the only native crop that is being disappeared by global capitalism. Native seeds are under siege from pole to pole. In Iraq, where the Tigris and Euphrates rivers come together to form the birthplace of agriculture, one of the very first acts of George Bush's neo-colonial satrap L. Paul Brenner was to issue the notorious Order 81 criminalizing the possession of native seeds. The U.S. military spread out throughout the land distributing little packets of GMO seeds, the euphemistically dubbed Operation "Amber Waves." To make sure that Iraq would no longer have a native agriculture, the national seed bank, located at Abu Ghraib, was looted and set afire. "
- http://www.counterpunch.org/ross11212007.html

To see a company attempting to become an arbiter of food supply by claiming property rights over plants that have evolved to the benefit of all the species on this planet naturally raises some questions and opposition.