Why is Wikipedia the first stop for plagiarists?

I was reading a digitally submitted paper by one of my students in 2006 and accidentally clicked on the text. Immediately my browser took me to Wikipedia. Sure enough seconds later I found the passage she had cut and pasted into her paper without change or attribution. Following that I escalated my stern warnings and threats to students about the evils of plagiarism.

Why do students gravitate to Wikipedia as the prime source from which to cut and paste their stolen content? Because it is unevenly written material and hence harder for a professor to detect using his innate plagiarism radar. Most of us academics can smell in an instant a paragraph lifted from a real encyclopedia.

Students know that Wikipedia is the best place to copy from because it is so easy to find and so poorly written. And who knows? Because anyone can change a Wikipedia article at any time, a professor trying to nail down the source of a plagiarist may not be able to find it. In fact a clever plagiarist may just go in and delete the copied text from Wikipedia after appropriating it into her homework.

But then most plagiarists are not clever.

By the way, according to the Times' Noam Cohen, at lease one department at one college, Middlebury's history department, has banned Wikipedia as a source to be cited in student work.