And your imagination regarding genetic diversity would be wrong: Roundup ready genetics have multiple generations, each with a smaller footprint in the genes of the host plant. Also, it's not as if this is being added to a single strain of soybeans or corn: There's quite a bit of genetic variation between different seeds with roundup ready genetics. It has to be, as the corn that has the highest yields in northern Montana is different than in Missouri: you have over a month in differences in relative maturity. Something similar happens in soybeans. If you want little genetic diversity, go look at plenty of non-gmo, completely Monsanto unrelated fruits (They just have a small veggie department).

Now, one has to be quite incompetent at spraying glyphosate to have significant blow over across the edges of fields: it's a very well behaved chemical in that regard. If you wanted to both make Monsanto look bad in this topic, you should forget about glyposate and think Dicamba. I won't bore HN with all the details, but even in Monsanto's new formulation, which supposedly makes the risk of hitting neighboring fields far lower, just picking a day where the weather isn't exactly right for the spray, or poor technique application, will lead to major damage in neighboring fields: The results might have been good in the lab, but they are not great in practice. It's arguably Monsanto's biggest piece of existential risk.