As I recall, a lot of photographers were very opposed to orphan copyright law that was making its way through Congress at one point. The gist of the argument as I remember it was the concern that people would make a very perfunctory attempt to contact the copyright holder ("Oh, we would have asked for permission but we didn't have a current address so we just went ahead and used it.")

And the overall situation with photography on the Web is probably much worse than writing. Even sites that wouldn't condone unattributed cutting and pasting of text routinely use all sorts of photos that I'm sure have been casually copied from somewhere on the Web.