1. A method of classifying entities, the method comprising: using a processor to perform acts comprising: recognizing occurrences of an entity in a plurality of documents; identifying a plurality of features in contexts of said occurrences, a first one of the features being derived from a first context of a first one of the occurrences in a first one of the documents, and a second one of the features being derived from a second context of a second one of the occurrences in a second one of the documents; calculating a sum of a plurality of weights, wherein each of the features is associated with one of the weights; making a first determination that said sum exceeds a first threshold; making a second determination that a label applies to said entity based on said first determination; and storing or communicating a fact that said label applies to said entity, wherein said features comprise membership in a list, and wherein said acts further comprise: choosing a subset of members of said members of said list based on members in said subset being estimated to occur more frequently in said documents than other members of said list; and comparing a string that occurs in at least one of said contexts with members of said subset; and making a third determination that said string represents a member of said list, said third determination being made (a) based on said string's being among said subset, and (b) without use of a filter that accepts all strings that are members of said list and accepts at least one string that is not a member of said list.