Fear is real but unfounded. You don't get sued by Monsanto for doing something accidentally. You really have to intentionally violate their rights.

The one case referred regarding this (Monsanto vs. Schmeiser) is widely misreported by anti-GMO and anti-Monsanto activists. See Wikipedia:

https://en.wikipedia.org/wiki/Monsanto_Canada_Inc_v_Schmeise...

The case is widely cited or referenced by the anti-GM community in the context of a fear of a company claiming ownership of a farmer’s crop based on the inadvertent presence of GM pollen grain or seed.[21][22] "The court record shows, however, that it was not just a few seeds from a passing truck, but that Mr Schmeiser was growing a crop of 95–98% pure Roundup Ready plants, a commercial level of purity far higher than one would expect from inadvertent or accidental presence."

Does the fear result from Monsanto actually suing them or from anti-GMO propaganda?