IBM is accusing Twitter of infringing on their patents. Twitter states through a patent agreement that it only wants to use patents as a shield and not a weapon. Twitter and IBM have yet to respond to any comments or questions. In March 2012, Facebook purchased 750 patents from IBM during the time a lawsuit had been filed by Yahoo for its claims of patent infringement. Yahoo and Facebook have not responded to requests for comments.

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IBM Takes Aim at Twitter, Claims to Have Patented Online Advertising – AdAge.com