If you paraphrased Harry Potter and published it, it would probably still be copyright infringement even if no single sentence in the novel remains unchanged.
It seems to me that it comes down to whether the work you made is a derivative work of someone else, particularly if you are directly taking their creative vision and adding nothing. Reproducing something in another medium easily could be the same thing as photocopying a book or selling prints of someone else's painting.
Copyrights are still much more debatable. The main defense for pro-copyright activists are that they're necessary for the economy. I tend more and more to the belief that the economy will change as a result -- a freer economy, but a different one.
there is no natural right to art
As a hobbyist photographer I can tell you - good photography is freaking hard.And IMHO, there are 2 kinds of people in this debate - the ones that can make good photos and the ones that bitch about the existence of copyright.
Reminds me of the "What Color are your Bits" piece http://ansuz.sooke.bc.ca/lawpoli/colour/2004061001.php