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In polite circles, they're known as nonpracticing entities. They buy patents from inventors and then bring lawsuits against companies they allege infringe on those patents. They're called nonpracticing entities because they have no plans to use the invention to make or sell products based on the patents.
To many tech companies, these nonpracticing entities are known pejoratively as "patent trolls." Since 1985 a few hundred nonpracticing entities have been involved in litigation with about 4,500 different companies, according to PatentFreedom, an organization that researches nonpracticing entities. Of all patent litigation, more than 70% is filed by patent trolls, says Daniel McCurdy, founder and chairman of PatentFreedom. McCurdy is also CEO of Allied Security Trust, a nonprofit association of companies that licenses patents in hopes of defending against patent infringement lawsuits.
Supporters say nonpracticing entities are simply helping inventors reap rewards for their handiwork. Whatever the case, they can make life difficult for the companies they target. "The number of defendants that are named in each lawsuit is growing dramatically," McCurdy says. Today there may be 10 or even 50 companies in each lawsuit but a decade ago the number was much smaller, he says.
Here are the 10 companies that have had the most lawsuits brought against them by nonpracticing entities since 2004, according to PatentFreedom.