Where Do Students Plagiarize from the Most?

I just found a list of websites that inform most of the student cheating. It's almost enough to make you lose faith in the younger generation to see where students mostly plagiarize from: 

Over all, the top eight sites for matched content were Wikipedia, Yahoo Answers, Answers.com, SlideShare, OPPapers.com, Scribd, Course Hero, and MedLibrary.org

 If they think that Wikipedia and Yahoo Answers are legitimate sources of information for college essays, this means we have been able to teach them nothing. Of course, if instead of churning out more idiotic paperwork, our bureaucrats occupied themselves with punishing plagiarism, the problem could be eradicated pretty fast.

There Is Plagiarism And Then There Is Stupid Plagiarism

When I was giving my lecture on Goytisolo, I informed students that he is my favorite writer ever and that I have published articles on his work. The most recent of these articles is scheduled to come out next month. I told them that I can't stop reading his Marks of Identity and Count Julian because every new reading brings something new to my understanding of his work. When answering questions about Goytisolo, I demonstrated an extensive knowledge of his writing.

So, please, tell me, what kind of a genius then goes and inserts sentences copied directly from Goytisolo's second most famous novel Marks of Identity into their own text without putting them into quotation marks and attributing them to the source? Is there any chance that I will not be able to distinguish a student's writing from that of one of the most important Spanish authors of the XXth century? What is the likelihood of me not recognizing Goytisolo's very distinctive second person narrator?

And most importantly, what's the point of alienating the professor in this way during the penultimate week of the semester?