RE: "trolls are firms that buy up patents with the express purpose of threatening others with infringement lawsuits"

You left an important part of the definition. This definition would certainly include PTSC. I added bold to key points. These are not my definitions and statistics, these are the Governments. Not a good sign for PTSC.

"Technically, trolls are known as "patent assertion entities" or "non-practicing entities" to distinguish them from firms or individuals who hold patents with the intention of making things with them.) In their most refined and abusive guise, trolls are firms that buy up patents with the express purpose of threatening others with infringement lawsuits. What makes this a perversion of the patent system is that their goal isn't to support the development of technology or produce goods for sale, which is the point of having patents, but to collect fees."

"It's not debatable that trolls are an economic drain. A White House economic study that accompanied the unveiling of its patent initiative cited an estimate that $29 billion was paid by patent defendants, mostly in the software industry, to troll-like plaintiffs in 2011. Only about 25% of that sum was plowed back into research or development. The very process of innovation can be stifled by patent litigation, the study said. Chien figured that 61% of all patent lawsuits last year were brought by plaintiffs fitting the description of trolls."

"Obama will be asking Congress to bring the standards of the International Trade Commission, which is prone to awarding injunctions like one it granted Samsung recently, into line with federal courts, where money damages, not injunctions, have become the preferred remedy for patent infringement."