The negative consequences of GMOs seem to have more to do with people's misuse of them or over-reliance than any evidence that they're dangerous. I'm concerned that, based on the evidence, it seems that some farmers may have been over-using pesticides because they had pesticide-resistant GMO crops.

The bigger issue is the hardest one to answer: what unknown consequences could we see? GMO crops are not created by the old-fashion breeding/blending/selection of traits. So the opportunity for unexpected outcomes would be higher.

For me, if GMOs are used because there are no alternatives to improve life on this planet in certain specific ways (eg starvation and malnutrition), then it's probably ok. Under circumstances where it's only going to boost profits, I don't see why would ever want to allow it.