Art lovers adore talking up the original. It's yet another way to elevate yourself, to in some way rise above the ordinary millions, to set yourself apart. For, say, antique collectors, it may be owning an original Tiffany lamp; for music aficionados, perhaps it's seeing Fleetwood Mac, before and after they broke up. Personally, I've only experienced this in a more removed sense. Last year, I went to the British Museum and felt my heart flutter to see such treasures as Shakespeare's First Folio and some Beatles lyrics handwritten by John Lennon and George Harrison. I thought it would be like this whenever I went to see some famous artwork in person, and often, it was. Seeing the Sistine Chapel in the Vatican or the David at the Galleria dell'Accademia in Florence were two of the most amazing moments from my study abroad year.
Then I went to the Louvre in Paris and, naturally, had to go look at da Vinci's Mona Lisa. Rather than the wave of awe I had come to expect, I felt disappointed. It may have been the frustration with the crowd in the overly packed room (the Mona Lisa has a hall to itself) or it could have been the fact that by that point I had been to been to a dozen splendid museums, five of them in the last week, and my sensory input was exhausted. But really, I think my dissatisfaction had more to do with the fact that, quite simply, I had seen it already.
Benjamin writes in "The Art of Mechanical Reproduction": "The situation into which the product of mechanical reproduction can be brought may not touch the actual work of art, yet the quality of its presence is always depreciated" (1235). Search "Mona Lisa" in Google Images, and beside several color-damaged copies you'll find many distortions and parodies of da Vinci's original painting. These may be thought of as effects on the historical testimony surrounding the original, insofar as "historical testimony rests on authenticity" (1235). Benjamin notes, too, that "what is really jeopardized when the historical testimony is affected is the authority of the object" (1235). The Mona Lisa, as the most famous artwork of one of the most famous artists, lends authority to other media that constantly uses its image--for example, a flier for a student club or an advertisement for flights to France. But for every use, its authority is diminished a little bit more.
By the time I saw the Mona Lisa for myself, its authenticity had been reduced so that it had reversed places with the affecters; the original seemed to be the copy, the representation of other, inauthentic art.
By contrast, less ubiquitous (but still well-known) art was more exciting to me. While visiting the Belvedere in Vienna, I turned the corner and saw Napoleon Crossing the Alps, and my delight here was, against all expectation, greater than when seeing the Mona Lisa.
Seriously, I think this can be found in any history textbook published since the dawn of color print.