1. A method comprising: receiving a plurality of user-generated content items; wherein the plurality of user-generated content items comprises: user-generated content items that reflect one or more non-controversial events, and user-generated content items that reflect one or more controversial events that are likely to provoke disagreement or uneasiness among viewers; determining that a subset of user-generated content items, of the plurality of user-generated content items, reflect a controversial event based, at least in part, on determining that a particular entity is referenced in the user-generated content of each user-generated content item in the subset of user-generated content items, determining that each user-generated content item in the subset of user-generated content items was received within a same window of time, and determining, based on an analysis of the user-generated content of each user-generated content item in the subset of user-generated content items, that the particular entity has provoked disagreement or uneasiness among viewers of the user-generated content; and storing data that defines the controversial event, wherein the data that defines the controversial event includes data that identifies the particular entity and the window of time; wherein the method is performed by one or more computing devices.