Fast Company writes an article about the problem of plagiarism on Amazon:
Amazon's policy is to remove offending content when it receives complaints of plagiarism. Erotica author Elizabeth Summers had at least 65 titles expunged when plagiarism allegations surfaced. Recently Robin Scott's books also disappeared from Amazon when writers complained. (Scott, which is almost assuredly not her--his?--real name, did not respond to requests for an interview over Twitter.) But this reactive approach isn't entirely effective.
Considering the volume of self-published digital work, it's inevitable that this will become an even larger problem, until some sort of content-matching anti-plagiarism process is applied to uploaded works (much like TurnItIn does for academic works). Other than the sheer volume of content that needs to be checked, though, these files are just text files. Any egregious plagiarism (some of the examples in this story are wholesale copying of books) should be quite easily picked up by a computer.
As it stands, large-scale plagiarism seems like an easy, low-risk (for now) way to make a quick unethical buck by sponging off the creative efforts of actual writers.
I've had two plagiarism threads appear on mailing lists I'm on, of people whose content has been resold on Amazon, and warnings about people submitting chunks of plagiarised work. Have any of you had any run-ins with plagiarism in your writing career?