Communication theorists have long presumed that the capacity of mass media was essentially fixed. This study investigates the relevance of this assumption in the digital environment, where production and broadcasting capacities have become nearly infinite. Examining 2 years of data from Twitter and electronic databases of news articles revealed some differences in the nature of constraint in the two environments. The daily volume of Twitter was more variable than online news coverage once cyclical factors were controlled. Interestingly, the volume of Twitter did not always increase in response to key events.