I spent three hours slumped in a lecture hall, probably with my eyes glazed over in boredom. The guy sitting next to me was busy reading papers and a text book. The couple in front of me were whispering snarky remarks to each other. The other guys nearby were rolling their eyes. Half an hour was spent wasted on vague rhetoric about the honor code. Another half hour was taken up by a fourth year student not so subtly hinting about beer parties while expounding the virtues of extracurricular activities in the Upper Valley. The last two hours were spent pounding in the sexual harassment policy.
It made some guys rather uneasy. How were they to interpret the subtle "cues" that indicated that a woman was uncomfortable? During the question and answer session, it was obvious that some students were strong feminists. It was always the man's fault, even if it was accidental. I'd say communication, not blame, is better to solve such conflicts. Only when the offending behavior continues after you explicitly say "no" (or when you get a third party to say "no" for you because you're not comfortable doing it yourself) do you go to a higher authority. I'm definitely not saying that you should try to solve the problem through ignorance and avoidance; I just find that ignorance and avoidance are not sufficient reasons to pin the responsibility solely on somebody else.
Of course, everything becomes more complicated when people's emotions are thrown into the mix. Trying to think logically about any problem is very hard when you're angry. You risk hurting someone else's feelings and making an enemy. Even I find it hard to solve a problem when I'm not angry because I'm not sure how the other person will react. Perhaps that is why I agreed with someone who said he'd rather avoid anything that might potentially become a problem by staying far away from the troublesome source.