A small, further, example of how genetically modified crops aren't quite as easy to control as their manufacturers would like: Greenpeace reports that even though Switzerland has had a ban on cultivation of GM crops in place for the past seven years, and prohibits importation of the same for either human or animal consumption, nevertheless genetically engineered oilseed rape (canola) has been found growing in a port area of Basel.
In total 136 canola plants were found, with 29 of them revealed by testing to be Monsanto's GT73 (RT73), a crop designed to be resistant to Monsanto's Round Up herbicide.
It's suspected that the GM canola established itself after seed fell to the ground while being transported on a barge or freight train.
Greenpeace sums up the threat:
GE canola is mainly cultivated commercially in Canada and in the US, where it has contaminated non-GE canola. In fact, herbicide tolerant GE crops are generally causing havoc for farmers that face new problems with superweeds. [...] GE canola contamination is already spreading in the European Union, even though it has not been approved for commercial cultivation in the EU. If released into the environment, the germination of canola seeds cannot be contained. A Swedish study has also shown that GE canola seeds could survive and be viable for germination even 10 years after their release into the wild.
Despite industry propaganda to the contrary (supported sadly by organizations such as the Gates Foundation), there is nothing that genetic modification has done to increase yields or promote drought tolerance or increase food security, that cannot be done more cheaply, with less environmental risk, by conventional crop breeding (though cannot be patented or profited from in the same way). Neither people at large, nor farmers ultimately benefit from GM crops, but the corporations making them sure do. It all comes back to money and control.