1. A computer-implemented method comprising: generating a channel for distributing content in a social network, wherein the content is related to a first topic; retrieving candidate content items related to the first topic from heterogeneous data sources; generating, with one or more processors, a model for a user comprising an interest of the user and prior interaction of the user with the heterogeneous data sources, wherein the interest includes the first topic; computing, with the one or more processors, an interestingness score for each candidate content item by summing properties of each candidate content item over single-attribute properties using the model and based upon interestingness of each candidate content item to the user and an extent to which the candidate content item's popularity has increased within a geographic area associated with the user; comparing the interestingness score for each candidate content item with a threshold for the first topic to determine which candidate content items have an interestingness score that exceeds the threshold for the first topic; generating a stream of content with content items that have an interestingness score that exceeds the threshold; populating the channel with the stream of content and providing the stream of content to the user associated with the channel; receiving feedback for the content items; and modifying the model based at least in part on the feedback.