1. A system for increasing accuracy of computer speech recognition comprising: a dynamic grammar builder computing device comprising one or more processing units and one or more computer-readable media comprising computer-executable instructions which, when executed by the one or more processing units, cause the dynamic grammar builder computing device to: obtain social network data occurring within a threshold timespan of a broadcast of media content; identify named entities from the obtained social network data that are trending within the obtained social network data; rank the identified named entities based upon the trending; and build a dynamic grammar comprising at least some of the named entities based upon the ranking; and a speech recognition computing device comprising one or more processing units and one or more computer-readable media comprising computer-executable instructions which, when executed by the one or more processing units, cause the speech recognition computing device to: perform speech recognition of spoken words, spoken by the broadcast of the media content, utilizing the dynamic grammar to create closed caption text for the broadcast of the media content.