I seriously doubt ALL of these offenders are paying Corbis or even negotiated waivers. DUmmies tipped them off to cause havoc. Mission “accomplished”.
http://images.google.com/images?hl=en&q=kerry+fonda&gbv=2
And in the case of AP, they reserve the right to deny licensed excerpts if it (pointing out fraud, bias, and error for example) could hold them up to public ridicule. Where does the First Amendment say anything about that? It definitely violates “fair use”.
Then fight it in court. It's really just that simple. Anyone has the right to ask you to stop doing something; if they decide to stop, then they haven't violated your rights.