1. A method for rating time-based broadcast media based on audience response, the method executed by a computer system and comprising: identifying a plurality of public social media content items broadcasted by a web-based social networking system; for each of a plurality of time-based media events, each corresponding to a chronological segment of time-based broadcast media, inferring an association between the time-based media event and at least a subset of the public social media content items associated with the time-based media event; selecting a time-based media event from the plurality of time-based media events for determining an audience response metric for the selected time-based media event; calculating, by a computer processor, the audience response metric for the selected time-based media event using at least the subset of the public social media content items associated with the selected time-based media event; and rating the selected time-based media event using the calculated audience response metrics.