Google tries to improve image tagging
By Mike DavisonThe Google Image Labeler is a feature designed to reward more accurate tagging of image content. The goal is for image based searches, reliant on tagging for search, to throw up more useful results and employs a points system to reward the user for tagging in a more conformist way.
http://googlesystem.blogspot.com/2007/05/google-image-labeler-is-more-exciting.html
