For some years now I have noticed the term "plagiarism" thrown around recklessly and with malice, but little else, aforethought. I think it is time to attempt an understanding of what the word is really all about.
The term plagiarism comes from the Latin plagiarius, meaning a kidnapper. It involves taking someone else's work and passing it off as your own. There are of course many ways in which one can use someone else's words and not be committing plagiarism. (Just as there are many ways one can testify about what someone else said and not be violating the hearsay rule, which many Judges in my experience seem unable to understand.)
The Clinton campaign, in a sign at how desperate it has become, recently accused Obama of plagiarism. This illustrates the gross misuse of the concept. When you use a line from someone else with that person's permission, as Obama did, it certainly is not plagiarism. A borrower is not a thief!
Also, much information is considered in the public domain and not subject to coyright. Like facts, for example. Trivia guru Fred Worth found this out the hard way. When the board game Trivia Pursuit came out, Worth discovered that about 30% of the questions had been lifted from his monumental "Trivia Encyclopedia" book. He filed suit over this, but the company won because a fact cannot be copyrighted. The whole story is recounted in chapter 11 of Ken Jennings wonderful book, "Braniacs".
I had a similar issue come up with quizzes I wrote for the FunTrivia.com website. At one point I got the idea of using questions from the "Who Wants to be a Millionaire" show, the idea being to study the % of right answers to the questions and thereby determine how well the show was doing at picking the proper level for its questions. However, the idiotic FunTrivia editors accused me of plagiarism and I had to withdraw those quizzes, thereby negating hours of work.
Similarly, you cannot copyright a sporting event. Thus, it is not improper to publish the moves to a chess game, since the moves cannot be copyrighted (Ron Chaika, are you listening?).
I suggest a moratorium on use of the word "plagiarism", so that in time perhaps its proper meaning can be restored to it.