1. A method of constructing a domain-specific sentiment classifier for classifying sentiment expressed by documents in a specified domain, comprising: scoring sentiments expressed by a plurality of domain-specific documents responsive to a domain-independent sentiment lexicon; identifying a set of high-sentiment documents responsive to the scoring; creating a domain-specific sentiment lexicon based at least in part on the set of high-sentiment documents; generating the domain-specific sentiment classifier responsive to the domain-specific sentiment lexicon; and storing the domain-specific sentiment classifier.