More on the category of simulacrum. It is an important category as it provides a way to counter the conservative attack on postmodernism that says doing away with representation and truth leads to a nihilistic world.
This conservative account holds that when images are no longer anchored by representation then we have the the substitution of the signs of the real for the real. The center of meaning is empty. Images now float weightless in cyberspace. We we are satellites in lost orbit in a world where images run together, become interchangeable and slip chaotically over each other.
Is this necessarily the case? Is Baudrillard the only option. Is either images that truthfully depict reality or free floating images? Consider this image:

Gerhard Richter, Administrative Building, 1964.
In this article on Richter and SimulacrumAndrew Ottwell says that in his photo paintings Richter took a found image, (news photo, documentary still, amateur snapshot, and at times his own photographs) then enlarged and reproduced the image on canvas. Richter's blurred and distorted pictures are simulacra in that the works make reference to "originals"--the source photographs--but do not duplicate them in the sense of being copies.
The Platonic account holds that simulacrum is a reproduction with the greatest degree of discernible difference from the original, but which is still recognizable as a derivation from a model. The copy makes you aware of the resemblances.
Deleuze's rethinking the simulacrum was concerned to overturn the system of values inherent in the Platonic hierarchy of original-copy as simulacrum. For Deleuze the simulacrum is not a "degraded copy,"---a poor copy of the original photograph. It is a literally different thing from the original. Deleuze's conception of the simulacrum makes you aware of the differences. The direction of evaluation is reversed: you become conscious of differences rather than samenesses.
Hence Richter's photo painting is a different thing from the photograph. It is not a representation of reality in the same way many consider photographs to be. The photo paintings are more about opposing and actively denying the historical "culture of painting" and the ability of the painting to represent a reality or to communicate meaningful content. This late modernist process is turns against representation as a model of reality in order to open a new space that affirms art's own difference from painting. Hence the process of differentiation is about ceding art mimetic function to photography and a conscious re-evaluation of representation.
The process is one of a deterritorialization involving a dissolution of old identities and territorialities and the unleashing of new images and meanings.
How does the simulacrum apply to our visual culture rather than individual painters or filmmakers? What kind of deterrorialization is taking place with the plethora of sexual images that now surround us? What is being deterrorialization by the entry of porn into consumer culture?
A suggestion. The image world of porn:
"... is a fictional, fantastical, even allegorical realm; it neither reflects the real world, nor is it some hypnotizing call to action. The world of pornography is mythological and hyperbolic, peopled by fictional characters. It doesn't and never will exist. But what it does do is to insist on a sanctioned space for fantasy."