re: andy warhol
to answer the about rhetorical question....
yes. andy warhol was once sued for the use of a photographic image.
it was the image of the four flowers.
he was sued by the photographer who saw warhol's painting reproduced in a poster in store window.
i just finished reading a very interesting book that spends some time on this subject.
THE CONTINGENT OBJECT IN CONTEMPORARY ART. its an mit press book that was published recently.
a good read.