1. A computerized method for automatically classifying videos based on faces discovered in the videos, wherein the discovered faces are not known to be associated with a particular category of videos, the method comprising: receiving, by a computing device, a video for classification; detecting, by the computing device, a face of a person in the video; determining, by the computing device, that the detected face is not associated with a set of known people stored in a known person database that is in communication with the computing device, wherein each known person from the set of known people is associated with one or more categories that can be used to classify videos in which the known person appears; comparing, by the computing device, the detected face to a set of unknown faces in an unknown face database in communication with the computing device, to generate a cluster of unknown faces that each match with the detected face by meeting a predetermined match threshold; identifying, by the computing device, a set of categorized videos based on the cluster of unknown faces; and assigning, by the computing device, one or more categories to the video based on categories from the set of categorized videos so that the video can be automatically classified based on the detected face even though the detected face is not associated with a known person.