Again, your approach to photo usage is commendable and beyond reproach. Although I know it is largely pointless, I reserve copyright on all my photos posted to Flickr. Every now and then I find someone using them without permission. Often I find that people have posted them to their blog, from which they get re-blogged and re-re-blogged ad infinitum. Usually the back link is obvious, but almost without exception they make it look like I posted my photo to their blog, which is mildly irksome, though nothing to get worked up about. I generally post a comment thanking them for liking my photo and only take them to task if they change the name/title of the photo.
People who bother to contact and either ask for permission or at a bare minimum inform me that they intend to use my photos are rare and I really appreciate it when they make the effort. On a couple of rare instances I have had people grab one of my photos and try to pass it off as being their own. One ***** even claimed that because he had modified it (cropped) that it was a new photo and he could claim copyright. Apparently he never bothered to read the part of copyright law pertaining to "derivative works" (copyright still belongs to the original holder). One of my Aussie friends here in Japan with some roughneck mates in Sydney, where the guy lives, offered to send them over gratis to lay a beating on the guy and the photo disappeared from his site.
Best of luck to you with the site.