I decided to give ImageRights a try - the service that searches the web for uses of your photos and helps you with claims for unauthorized uses. They have a free basic membership so I figured what the heck. I am impressed with the scope of what they do - I uploaded ~400 images and there must be jillions of photos on the web, how can they possibly do all these comparisons? Does anyone know the algorithm they use to make the task manageable?
Be prepared for a lot of false positives. Do you have any idea how many people have taken and published photos of the famous scenes in Arches National Park, of Himeji Castle in Japan, and so on? These are (quite rightly) flagged as possible matches and you must go through them one at a time. Then there are some "matches" that are just plain funny, such as this one.
