1. A system for classifying documents in a collection of documents according to their intended readerships, the method comprising: a computer configured to: select a document in the collection of documents; determine a characteristic of the selected document, the characteristic being: misleading when the document includes one or more features that are determined to be for a purpose other than reading the document, commercial when the document includes features that are presented for a commercial purpose, or personal when the document includes features of a personal opinion; classify the selected document as misleading, commercial, or personal according to its determined characteristic; and repeat the steps of select a document, determine a characteristic of the selected document, and classify the selected document for additional documents in the collection; wherein at least some documents are classified as misleading, at least some documents are classified as commercial, and at least some documents are classified as personal.