First off, a field being used for cattle forage ideally should have between 100+ varieties of grasses. So alfalfa should only comprise a percentage of that. Not that that is the reality of things, but that is the ideal. Before agriculture came along, a single prairie might hold 1000+ varieties of forage. The animals recognize these and elect them based on their dietary needs and/or preference.
Second, if genes like the terminator get out of control, just like that you could lose an entire staple crop (which may not be a bad thing in the cases of corn and soybean!) from the face of the earth. Since humans rely heavily on grains to feed the 7 billion+ people on the planet, obviously that may be the quick way to overpopulation reduction. Still, not a nice image of the future, not one I'd want my baby brother and sister growing up in. We've already seen wild populations of alfalfa contaminated with GMO genes in places like montana. The point is that when it comes to these types of things, better safe than sorry, better not to assume these bastard genetics are innocent until proven guilty. They should be guilty until proven innocent.
Third, the point I see a lot of people missing here is that western society is based on property rights, without that everything else crumbles. GMO's are a clear infringement on the property rights of others. Since the pollen from the source GMO's contaminate non GMO crops so that they have the unwanted GMO genes in the next generation of seed, the seed is worthless to the non GMO farmer, in other words his/her property rights are being infringed by companies like monsanto. And then in the very twisted form of these souless companies, they turn around and sue the hell out of the farmer who wound up planting bastardized crops the next year. It should be the farmer suing MOnsanto for contamination of his pure genetics.
Fourth, GMO's do NOT increase yield, instead they protect from loss of yield. That is very distinct, and a very important distinction to make. GMO's are pushed as yield improving but in reality all they do is allow the "farmer" (aka ignorant, selfish, asshole, tool) to dowse the plants with poison without it dying, that is IT. Of course in even realer reality all it does is to make farmers dependent on monsanto each year for the seed that the farmer used to produce themself. Control the food and you control the population and all that...
Fifth, the concern is not as much the effect of GMO foods on the body, that is very selfish and narrow minded, the concern is in the aforementioned natural catastrophe and the ensuing starvation that would result from the sudden loss of one of the worlds staple crops (rice, corn, wheat, soy, etc). Also at risk is the philosophy of private property rights.
Sixth, F monsanto in the A.