The problem of excessive patent protection is at present best illustrated by the software industry. This is a progressive, dynamic industry rife with invention. But the conditions that make patent protection essential in the pharmaceutical industry are absent. Nowadays most software innovation is incremental, created by teams of software engineers at modest cost, and also ephemeral—most software inventions are quickly superseded. Software innovation tends to be piecemeal—not entire devices, but components, so that a software device (a cellphone, a tablet, a laptop, etc.) may have tens of thousands, even hundreds of thousands, of separate components (bits of software code or bits of hardware), each one arguably patentable. The result is huge patent thickets, creating rich opportunities for trying to hamstring competitors by suing for infringement—and also for infringing, and then challenging the validity of the patent when the patentee sues you.
It's definitely worth reading the full article beyond just Judge Posner's quote.