It wouldn't be a full day here at Engadget without someone suing someone else for patent infringement, and thankfully Verizon has stepped up to the plate to provide our daily dose of entertaining legal shenanigans. The telecom giant has filed suit against VoIP provider Vonage in Richmond, Virginia's U.S. District Court, claiming that certain aspects of Vonage's Internet telephony business -- specifically its methods for interfacing between packet-switched and circuit-switched networks, billing customers, detecting fraud, and providing enhanced calling services -- violate at least seven of Verizon's closely-guarded patents. What really seems to be getting under Verizon's skin is the fact that Vonage has added 1.1 million new customers in the past 15 months -- many of whom are claimed to be "Verizon's former customers" -- by "aggressively marketing and advertising services made with Verizon's appropriated intellectual property." Vonage, of course, denies any wrongdoing, and claims in language we've heard so often before that it will "vigorously defend the lawsuit;" investors, however, don't seem to be quite as sure that Vonage is in the right here, as evidenced by the 12% tumble that the company's stock took today.

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