1. A method comprising: collecting usage data that indicates how users interact with annotations contained in documents presented to the users, wherein said annotations are associated with entities contained in the documents; based on the usage data, generating weights for features of a feature vector; identifying a set of identified entities within a document; determining a ranking for the identified entities that belong to said set of identified identities based, at least in part, on (a) feature vector scores for each of the identified entities, wherein the feature vector scores correspond to features in the feature vector; and (b) the weights generated for the features of the feature vector.