As a gardener, I'm a proponent of heritage seed crops and open pollinated varieties that will breed true from saved seed. This allows me to grow quality food crops year after year from saved seed stock.
Concerning GMO and hybrid food crops, the seed stocks are all controlled by corporations with patents on their genetic handywork; you cannot save seed from GMO crops because it will either be sterile, or will also not breed true to the original plant; so you have to purchase new seed year after year after year to maintain that food crop. This is fine and dandy while that corporation continues to sell and produce that seed, but what happens when they no longer do so and all your saved seed from that crop is worthless?
Beyond that, I have general concerns about genetic manipulation of plant genome where genes from entirely different kingdom of life are introduced. We've seen this in food crops such as corn and adding genes from bacteria to produce a corn that provides it's own built in pesticide. I worry about potential long term consequences to our health and food supply in general. This is a new level of genetic manipulation well beyond traditional cross breeding and trait selection practices that have been used for thousands of years.
However I am not a scientist and I must trust them and the organizations that they work for that they have the best interest of humanity in mind when producing these food crops. I am at their mercy, as are all of us. For the greater good, as it were. How much faith do you have in Monsanto's altruistic nature?