Avoid unpleasant situations....

Within academia, plagiarism by students, professors, or researchers is considered academic dishonesty or academic fraud, and offenders are subject to academic censure, up to and including expulsion. In journalism, plagiarism is considered a breach of journalistic ethics, and reporters caught plagiarizing typically face disciplinary measures ranging from suspension to termination of employment.
For professors and researchers, plagiarism is punished by sanctions ranging from suspension to termination, along with the loss of credibility and integrity. Charges of plagiarism against students and professors are typically heard by internal disciplinary committees, which students and professors have agreed to be bound by.
(Source: Wikipedia)

P.S. Don't forget that professors also have access to the internet ;)