Greenpeace destroyed a GM wheat crop study by CSIRO, a government research department. It's a shame because it would have found evidence whether such GM crops had problems.
"Greenpeace says it has taken action because of concerns over health, cross-contamination and the secrecy surrounding the experiments." facepalms
Source: http://www.scientificamerican.com/article.cfm?id=genetically...
Every day, an unique, genetically modified plant is born, because a gamma ray from the outer space hit its DNA and altered it in a non-predictable fashion. 99.99999% and maybe more of these mutants are harmless and probably simply die.
The alteration of genes can happen on your very own garden and without any safety measures. Some of these natural mutants may even be dangerous and nobody cares.
Is this randomness and total lack of safety better than a scientist armed with knowledge and a place to conduct experiments?
That being said, I think the fear is that scientists potentially have the motive to create dangerous/unhealthy strains of plants - a motive which miRNA and transposons (god-willing) do not have.
1. Monocultures are bad. GM crops don't have to be monocultures but they generally are for a number of business reasons that have nothing to do with food production.
2. GM crops cross-pollenate thereby spreading patented genes to non-GM fields. The owners of these non-GM fields are then sued and forced to switch to GM crops.
3. GM crops business models are often built around vendor lock-in. Historically vendor lock-in has been bad for software development and I think we can extrapolate these results to farming.
4. Cross pollination to wild-type is generally disruptive to the environment short term (for example consider what happens when wild plants produce pesticides from a GM gene). The effects are probably no different than introducing an invasive species. Generally people see this as a bad thing (snakes in Hawaii for example) and create laws to prevent it from happening. http://en.wikipedia.org/wiki/Invasive_species
5. There is a big difference between point mutations and transgenic plants. http://en.wikipedia.org/wiki/Transgene
I think GM crops can be developed, used in a safe manner and provide a great benefit to humanity, but that is not the current state-of-affairs. There are good reasons the EU regulates GM crops as much as they do.
The patent thing is a separate problem. Patent law in many areas is pretty bad.