1. A computer-implemented method, the method comprising: receiving a request for sponsored content for presentation with a multimedia content item, wherein the content item is included in a document; selecting a plurality of keywords for the content item wherein a first keyword of the keywords is selected based on historical user interaction with the content item when the content item was provided as a search result responsive to a query comprising the first keyword, and wherein a second keyword of the keywords is selected based on analysis of the content item; for each of one or more candidate sponsored content items: calculating a respective first score based at least partially on a comparison of the candidate sponsored content item to one or more of the keywords; calculating a respective second score based on, at least, a comparison of the candidate sponsored content item to content of the document and based on a profile of an owner of the document; calculating a respective final score based on, at least, a weighted combination of the respective first and second scores in which the first and second scores are weighted differently, and in which a weight of the first or the second score is based at least partially on a measure of past user interactions with the candidate sponsored content item when the candidate sponsored content item was presented with the content item; selecting one or more of the candidate sponsored content items based on, at least, the candidate sponsored content items' respective final scores; and providing the selected sponsored content items for presentation with the content item.