1. A method comprising: generating a topic space based on a plurality of microblog entries and click-through data associated with a plurality of media items in a media domain, the microblog entries being unrelated to entities accessing the microblog entries; receiving a microblog entry from a social stream domain; determining, by one or more processors, based on the topic space associated with the social stream domain and the media domain, a topic that is associated with the microblog entry; and determining, based at least on a tag of one or more media items in the media domain being in common with a word of the topic, that the one or more media items in the media domain are associated with the topic.