I don't think there's been any lawsuits over small-scale non-commercial infringement, but there have definitely been lawsuits against farmers regarding the propagation of patented crops.
Note that plants aren't special in this regard. If you buy a computer or a car or a lamp or soda that contains unlicensed patented technology, then you're in violation of the patent and are theoretically liable for damages. (Note: not a lawyer, I could be wrong, etc.) This rarely comes up, because it's rarely worth going after individuals, but patent law is pretty broad. When you buy something that is legally licensed, you're covered because the manufacturer obtained a license that covered all users of the product, not just themselves.
A computer or a car or a lamp or soda is different from a plant because they do not propagate and create new versions of themselves. Well, maybe the soda but I am rather sure neither the car of computer can do it. Well, a 3rd printed computer could but lets just say that self-propagating patented products are legally messy things. As a consumer or business owner, there is not much one can do beyond keeping ones eye close and hope no one will sue. If they do sue, hope that the judge is a fair minded person that will consider intent and what is human possible regarding patent knowledge.
>A computer or a car or a lamp or soda is different from a plant because they do not propagate
Which is why Monsanto and other companies tried to introduce "terminator seeds": plants who are sterile, so they a) guarantee more profits and b) the IP becomes easier to protect. The technology hasn't been introduced because protests were too large.
There is nothing stopping Monsanto in selling those in the US or markets outside of India.
However, in lands commonly plagued by famine, I could see the argument that terminator seeds would impose a serious security risk to the population. If for some reason the harvest fail, then the farmers is out of both money and seeds to survive for the next year. There would be nothing to fall back on. Terminator seeds would become de-facto time-bombs that are triggered during bad years, and I would understand a government depended on farming to outlaw such seed.
Correction: Below commenter is right that there might be legal issues in using the seeds even outside countries that has explicitly outlawed it. My fault for just reading the sources and not the whole Wikipedia section.
>Initially developed as a concept by the United States Department of Agriculture and multinational seed companies, Terminator seeds have not been commercialized anywhere in the world due to opposition from farmers, indigenous peoples, NGOs, and some governments. In 2000, the United Nations Convention on Biological Diversity recommended a de facto moratorium on field-testing and commercial sale of terminator seeds; the moratorium was re-affirmed in 2006. India and Brazil have passed national laws to prohibit the technology. [1]
The difference, of course, is that your neighbor's patented computer/car/lamp/soda won't spray pollen out that hits your computer/car/lamp/soda, causing it to produce little baby patent-violating computers/cars/lamps/sodas that you can be sued for. Yet exactly that can happen with crops.
According to that page, it only applies to sales that were originally authorized. The way I read it, it means that is Ford licenses a patent for its buyers, the patent holder can't then go after buyers of used Fords, even though Ford may not have explicitly licensed used buyers. It does not, however, protect any Ford buyers, new or used, if Ford failed to license the patent at all.
