Like to see a test case!
No need for a test case, these things go to court on pretty much a weekly basis. It's much easier to nail people for publishing photos without permission than distributing MP3's via filesharing.
I have no issue with people using my pics around the internet on forums, blogs etc although I prefer they are linked from my Flickr so at least can be traced back as my work. It's when it's used on professional sites and in printed magazines without permision or even a credit you can nail them.
Nick