As I noted before, in addition to his invaluable work overseeing Arts & Letters Daily, Denis Dutton maintains a personal site with access to his own writings. Among the recent highlights is a link to his entry on Forgery and Plagiarism for the Encyclopedia of Applied Ethics. Here is the conclusion, charting the relative impact of plagiarism and forgery on the historical record:

The situation with regard to historical understanding and plagiarism is different. Since forgery is usually attributed to a historically important figure, forgery distorts and falsifies our understanding of art history. The historical damage of plagiarism, on the other hand, is normally minimal because the plagiarist is stealing contemporary work for his own designs, to help his own reputation. The successful forger, in contrast, affects our view of historically important artists and creators.

For some cynics, the only real damage done by forgers is what they inflict on the bank accounts of rich art investors. However, it is a mistake to see forgery in this way. Art is not just about beautiful things, it is about the visions of the world recorded in centuries past. The illustrated record of those visions can be corrupted by the skill and subterfuge of a contemporary faker. The extent to which this subtly distorts our grasp of our forebears’ understanding of their world remains to be seen. But the skilled handiwork of people like [forgers] van Meegeren and Hebborn, when it succeeds, will distort our understanding of the history of graphic representation just as surely as a document forger’s skill might alter our understanding the the history of ideas. Forgery is not a victimless crime, even if the forger is successful and 'no one knows.' For the real victim is then our general understanding of the history of art and of human vision. As noted earlier, many forgeries are recognized for what they are by later generations. But is a perfect, undetectable forgery possible? We can never be certain. The perfect forgeries existing among us are unknown, undetected aliens.

Of related interest: Dutton's article on Authenticity in Art for the Oxford Handbook of Aesthetics.

My favorite fictional consideration of fine art forgery is the late Robertson Davies' What's Bred in the Bone, in which Davies' protagonist Francis Cornish finds the truest expression of his own artistic impulses and comes to terms with his personal history through the creation of "perfect" forgeries of the work of previously unknown anonymous medieval masters.

The question of plagiarism and "fair use" of copyrighted material is apparently a hot topic among crafters of haiku. Haiku being so short by definition, it has been suggested in some quarters that to quote any portion of the poem constitutes a copyright violation. A related phenomenon is so-called "deja-ku" in which haiku by different authors bear close resemblance to one another. David Giacalone (who just keeps reappearing in these pre-posted posts) combines his interests in law, ethics and haiku in this essay: Haiku and the Fair Use Doctrine.