LIfeHacker reports on TinEye, a search engine that finds images across the Web. The account is free and permits you to upload an image and then locate other instances of it. The LifeHacker author used the service to find images of a co-worker based on a headshot he knew had been used several times, with mixed results. Even so, TinEye seems to be an interesting tool for tracking the use of images or the activities of individuals on-line.

Image Search: TinEye Finds Instances of an Image Across the Web