I've had a couple of instances now where I've found someone has used one of my images without permission.
Because of the Photobucket problem I am re-uploading my pictures to other storage places and I want to "watermark" them so that I can find if there is any infringement in the future. They already have a visible watermark on them.
What I want to know how to do is to put a unique string of text in to the picture information (EXIF data?) so that I can search for that to pull the images up in Google Images.