To some degree, belief in integrity motivates our negative response to "copy-catters" as well. Consider the fact that, as magical thinking goes, nobody does a Picasso like Picasso. In the same way that no one quite cooks baked macaroni and cheese like mama does. Our quest for the authentic is rooted in empathetic responses comparable to the "Golden Rule." Nobody likes to have their thunder stolen, so to speak. So if I drew a crayon drawing and you claimed it was yours, your lie devalues my work. If you copied my crayon drawing and claimed it was your work, your lie devalues my creativity. An understanding of some of the process of creativity allows most art enthusiasts to respond empathetically with the same type of horror as one would experience if they'd discovered their own work of art had been replaced by an exact duplicate by another person's hands. It's not so much the percentage of similitude or the differences that infuses the honest anger as it is the little white lie that hides behind the fact that it looks like an original but isn't. That's what angers enthusiasts, I believe. the fact that a person would "lie" about something so personal as art inspires our empathy.

I wonder if the new medium of the Internet may have an effect on our essentialist tendencies? When a byte-by-byte copy can be made of any "object", what constitutes the original? Taking music-sharing for example, one doesn't go looking for the original mp3 file that contained a song, nor does one even look for a file that has been copied a known, low number of times. Sometimes the lossy-ness of a file has no relation to how many times it's been copied.
Maybe as more and more commodities are duplicable in an exact and lossless manner, our value on authenticity will go down both on- and off-line.