Some interesting thoughts by Timothy Burke on remixing, plagiarism and their relationship to creativity and originality over at Easily Distracted. Read the comments too.(Andrew Orlowski, a particular skeptic of remix culture, has also written on the topic here.)
As Burke notes, there are "examples of visual media where the remixes were inspired, entertaining, and emotionally engaging." However, at the same time "remixing" so often becomes an excuse for misappropriation. An additional problem is that of giving credit where credit is due. We've had hundreds of years to figure out what's appropriate in different contexts within print—where and how credit should be given and in what form. For photos, video, music, and even code proper and legal behaviors are far less clear.