[loup-vaillant]

The lone inventor probable doesn't exist at all. We often observe that ideas are found independently and nearly simultaneously by several people. (IIRC, pg says so in one of his essays.) That would mean that when an ideas is ready for prime time, it will be discovered anyway.

Assume that the absence of patents could send some would be lone inventors to poverty, while allowing the ideas they would have found to be found anyway. That's probably not OK for most people. However that's also a net benefit for society, and so is most probably OK. But "benefit for the society" is a vague and abstract notion. The "lone inventor" is something you can understand, feel, identify yourself with. I think a good argument against software patents would have to make people cry just as much.