Patent troll is a derogatory term used to describe a patent owner, frequently a small company that enforces patent rights against accused infringers, but does not manufacture products or supply services based on the patents in question. A patent troll may represent an entity who performs research or manufactures products incorporating the patented technology, though the troll itself does not.Patent trolls focus their business on the enforcement of intellectual property rights.
The key point of contention against patent trolls is not their non-practising status, nor that their assertions are necessarily invalid, but rather that "they are in a position to negotiate licensing fees that are grossly out of alignment with their contribution to the alleged infringer’s product or service". Indeed, the core controversy is over equitable issues rather than legal issues. In particular, some believe that patent trolls have an unfair advantage over manufacturers since they are relatively immune to the burdensome litigation tactics which are a traditional front line of defense by large entities against small entities. Others warn that tying the nature of a property owner to the nature of property rights poses a fundamental threat to equal protection under the law, notably in the US, under Article 1, Section 8 of the Constitution.
Some allege that use of the expression "patent troll" is primarily a public relations tactic that large corporations use to intimidate individual inventors in an effort to tilt the playing field in their favor. In this context, it is sometimes noted that the same large corporations that criticise patent trolls collect significant revenues enforcing their own patents against smaller or emerging competitors, including patents relating to technologies that they themselves do not implement in the marketplace.