Judge Richard Posner writes about the US Patent system:
Moreover, a firm that can get along without patent protection may have compelling reasons to oppose such protection because of fear of how its rivals may use it against the firm. A patent blocks competition within the patent’s scope and so if a firm has enough patents it may be able to monopolize its market. This prospect gives rise to two wasteful phenomena: defensive patenting and patent trolls. Defensive patenting means getting a patent not because you need it to prevent copycats from making inroads into your market, but because you want to make sure that you’re not accused of infringing when you bring your own product to market. The cost of patenting and the cost of resolving disputes that may arise when competitors have patents are a social waste.
Patent trolls are companies that acquire patents not to protect their market for a product they want to produce — patent trolls are not producers — but to lay traps for producers, for a patentee can sue for infringement even if it doesn’t make the product that it holds a patent on.
