I'm afraid that this post is 95% siimiliar to an article written by P.J.Levi
I thought I would offer a brief teaching idea, especially for those who have their students submit papers to SafeAssign or some similar plagiarism-detection software.
I just had one of my own students email me, quite frantic that SafeAssign gave him a ~30% matching score. SafeAssign compares a student's paper to all other students' papers and the Internet. But, he assured me, I didn't copy anything!