[1] This question continues to be debated around the world.  Some consumers, especially many European and Japanese, are not accepting food made from GMOs.  A growing minority of US consumers is now raising serious questions as well.

[2] Before trying to answer the question posed in the title, I should define what is generally meant by GMOs.  They are Genetically Modified Organisms that have been produced by inserting a piece of foreign DNA into the nucleus of a recipient organism.  The new DNA is integrated into chromosomes of the recipient so that it modifies the recipient by adding the trait(s) from the donor organism.  This transfer is done by extraordinary means rather than by the traditional transfer that has been accomplished by hybridizing individuals within a species. 

[3] It is common practice to evaluate the usefulness of a new approach by assessing its risk or cost/benefit ratio.  Therefore, one way to assess the "market-readiness" of GMO foods is to compare the benefits of such foods to the real or projected risks associated with them.

[4] From a consumer perspective, the benefits are likely to be either MORE food or DIFFERENT, presumably more nutritious, food.  For currently available GMOs, there are no easily identifiable qualitative differences, so consumer benefits must be quantitative.  However, for consumers in the industrialized world, more food offers no real advantage or benefit because access to food is already taken for granted.  Thus, it can be concluded that GMOs currently offer little or no benefit to these consumers. 

[5] Who then does benefit from GMOs?  Given the current financial status of most crop producers in the "Upper Midwest", it appears that many of them aren't benefitting very much either, if at all.  That pretty much leaves the benefits to those selling the products and the chemicals needed to grow them. 

[6] Thus, we can conclude that there is very little benefit from the GMOs to the consumer or the producer.  Actually many or most consumers don't even know when they are eating GMO food, because there is no labelling to inform them relative to GMO content.

[7] What about the risks?  The potential risks can be grouped into a minimum of three categories; food safety, reduced biodiversity of our already limited diets and crops, and pesticide resistance.  The three federal agencies which have jurisdiction, FDA, USDA, and the EPA have all agreed that GMOs are "essentially equivalent" to improved crops and animals produced using traditional means.  That designation means that no special tests are made on the GMOs unless suspected allergens are involved.  Further, all of the data that are available to these agencies comes from the owners.  There are no independent/third party testers for these food products.

[8] The second category of potential risks is reduced biodiversity of our diets.  The causal basis for this concern is at least two-fold.  One is that GMO research and technology is quite expensive so only a few of our already limited food crops will get much attention.  Secondly, as a few of these products do become quite popular, we will continue to face intensified "monoculture" of crops used to produce our food, especially highly processed food.

[9] The last category of risk listed above is well beyond the potential stage.  There are several well documented examples of plant species which are now relatively unaffected when sprayed with the well-known herbicide "Roundup".  When it was first introduced about 20 years ago, Roundup would kill virtually every plant that it came in contact with.  Similarly, there are also documented cases of resistance to BT, the natural insecticide produced by BT corn and cotton.  Of special concern is that the BT compound is a very effective "tool" for organic growers to manage certain of their insect problems.  When targeted insect populations develop resistance to BT, these producers essentially have no alternative control measures available to them.  A related problem is that the effects of these BT plants are not limited to target insect populations.  The monarch butterfly is a good example of impact on an unintended target.

[10] Thus, there is considerable POTENTIAL risk, especially when compared to minimal consumer benefits.  Thus, in the long term, planting GMO crops on large amounts of our crop acreages poses real dangers that can accumulate into major threats to crop production and the natural resource base supporting it.  Given the above analysis, the calculated risk/benefit ratio suggests that we should continue to be cautious rather than growing GMO crops on rapidly increasing acreages.