[polymatter]

You can be liable for triple damages if the court decides you knew about the patent and infringed anyway. Normal damages if you did not. I believe independent invention is meant to be so rare as to be suspicious (despite many documented cases where this happened).

The (supposed) purpose is to give an incentive to inventors to freely broadcasting their inventions, by giving them a monopoly on it so they can recoup their investment. Without that incentive, inventors would keep their inventions trade secrets.