I've always been intrigued by recognition software because I cannot imagine the logic that goes into all of the algorithms. Whether it's voice, face, or other types of detection, people look and sound so different, pictures are shot differently, and from different angles, I cannot fathom how it's all done. Since I already covered booby nudity detection with JavaScript, I thought it would be worth some time to explore face detection. Facebook uses it, so maybe it has application in your websites.