Patent Troll

Patent lawsuits are especially common in the tech world for a few reasons, one being that software is patented, rather than copyrighted. The language used in software patents also tends to be more abstract than that of pharmaceuticals, for example. When aggressive patent litigation emerged in the 1990s, many companies - most notably, Microsoft - paid hundreds of millions of dollars in settlements and awards.

As a result, many tech companies started amassing patent stockpiles to help protect themselves against litigation. These stockpiles, known as defensive patents, can help prevent suits between companies because each has enough patents to repeatedly sue the other. This is what occurred when Yahoo sued Facebook for patent infringement on 10 patents in March 2012. Rather than settling, Facebook countersued with 10 of its patents.