This search engine creates a finger print and goes to search out through its database of pictures to see if they could find a match.  This might be used by AP and other authors to search for people who may be using their pictures without approbation or copyright infringement.


From this article: http://arstechnica.com/news.ars/post/20080819-tineye-image-search-helps-ferret-out-copyright-ripoffs.html