None of this will be new to the farmers out there (indeed, there is already an ongoing lawsuit), but this episode of NPR's Planet Money podcast covers a problem that can arise when one farmer's pesticide winds up killing another farmer's crops. Here's a summary of the story:
“Farmers are in constant conflict with the weed. Some have turned to a powerful pesticide called Dicamba. Dicamba kills the pigweed, but it also kills the neighbors’ plants, including farmer Mike Wallace’s crops. The conflict was no longer farmer versus weed, but also farmer versus farmer. When his neighbors illegally sprayed the pesticide, Wallace reported it. After harvest, Wallace was shot and killed.”
The story is a powerful lesson about externalities that can arise with herbicide resistant genetically engineered crops (this one is largely negative, but note that GE Bt crops can create positive externalities). Who's to blame in this case? Monsanto for releasing GE Dicamba-resistant seed before a new version of Dicamba was released? Regulators for their slowness in approving the new Dicamba? Farmers who improperly used and applied the old version of Dicamba? You'll have to listen and form your own judgement.