Not to defend the patent system too much, my experience with it mostly involves a second parties trying to patent ideas that others came up with, but there seems to be a bit of a selection effect problem here. Of all the people who consider copying something patented, some fraction of them are stopped by the presence of the patent. Of all the people who independently invent something you would expect only a very small percentage to be stopped by a patent. Also, someone who knowingly copies someone else's work knows to hide the fact.

So unless we know what percentage of people were stopped from copying someone else's work without the need for a lawsuit, this study alone doesn't tell us very much about the social costs and benefits of patents by itself. I tend to believe that our patent system is too strong and I might very well mention it in discussions with proper caveats, but we need more research.