Just going to store some bits and bobs in comments. There's been quite a damning-by-association and innuendo developing. This, via this for example. I just wanted to pick up on the 'Pickett buried rat evidence' thing. Quoting from a review paper that Logikblok sent through:

In the late 1990s, Ewen & Pusztai (69) conducted studies on rats fed potatoes engineered to express an introduced lectin gene from a snowdrop plant (Galanthus nivalis), intended to reduce insect damage. After feeding, they observed stomach lesions in the rats and concluded that “the damage to the rats did not come from the lectin, but apparently from the same process of genetic engineering that is used to create the GM foods everyone was already eating” (211). This study and its conclusions were strongly criticized by the scientific community (186), because the study was conducted with too few animals and inadequate controls. Following the initial announcement of the findings to the popular press, the original study was published in the Lancet to provide researchers an opportunity to view the data. But the data in the paper left researchers unable to draw firm conclusions (134) or confirm or deny results. The U.K.’s Royal Society criticized the study for lack of proper controls. In the same issue of Lancet in which the paper was published, Dutch scientists concluded the observed toxic effects might be due to nutritional differences between control and GE potatoes, not from the GE process (133). To reach firm conclusions, experiments should be repeated on larger numbers of animals with proper controls. Notably, this product was not marketed and the results do not extend to safety analyses of other GE crops. (See section 3.4)

But then, the scientists would say that, wouldn't they? This is all sounding wearily familiar...