I also went to Stanford and when I took a beginning level CS course a student in my year was caught cheating. He copied a problem set from someone else and was later suspended for a quarter. Stanford has a judicial review board composed of students that make the final decision in cases like these and he was still punished. Everyone was warned by the professor at the beginning of the class that the CS department catches the most students cheating every year b/c every problem set is electronically reviewed for ways it might have been copied.