In days gone by such activity was commonplace and largely without much risk to the person conducting the scan. You well know that those days are long gone. But don't tell that to one particular university professor.
When you read the daily log over at SANS Internet Storm Center you'll see that the professor in question has actually ordered his students to conduct "a remote security evaluation of one or more computer systems. The evaluation should be conducted over the Internet, using tools available in the public domain." The assignment accounts for 15% of the students' overall grade.
This is one professor who needs a course in ethics, as he is apparently without much conscience -- not to mention common sense and awareness of the legal ramifications!