There have been a lot of good posts so far.

To address the original question - there is no hard and fast answer. ISAF Case 50 (see .pdf]http://www.sailing.org/tools/documents/casebook2006supplement-[909].pdf )
reads on this matter. The protest committee must decide whether S(tarboard) bore away early, or P(ort) failed to keep clear. If RRS 16.1 applies, the PC must also determine whether or not sufficient room was given. The variables involved (boats, seas, wind) are too great to embody in a rule, so it is left as a judgement call.

Regarding why we seldom protest an infraction, I think there are multiple reasons, including:

1) Lack of experience. People seldom have protests and simply don't know how to proceed, or are scared to. There's only one real solution to this, though, and that's to protest and learn.

2) Lack of motivation. Let's face it - a protest hearing is a hassle. It takes time and effort that we would much rather spend packing up and socializing. If you read the preamble to the rules, however, you'll see that we are expected to both "follow and enforce" them. If we fail to enforce the rules (don't protest), then we cannot honestly complain when others do not follow them.

3) Lack of maturity. Sadly, I think this is a big component. In these politically correct times, a protest is often taken as an accusation of cheating. It isn't. Despite my best efforts, I do occasionally foul someone, or hit a mark, or am over early. In those events, I own up to my mistake, take a penalty, and move on (at least - I try to move on <img src="http://www.catsailor.com/forums/images/graemlins/blush.gif" alt="" /> ). I believe that when a protestee takes offense, or worse - blames the protestor, then he simply needs to grow up.

That said, I do protest far more often than anybody else in my local club - and I take some heat for it. Recently I protested a boat in a different fleet, and the skipper couldn't believe it. He felt that since we were not competing against each other, he should be allowed to get away with the foul. He exonerated himself on the water though, and (aside for some discussion at the social) that was the end of the matter.

My position is: If you foul someone, take a penalty. If someone fouls you, protest.

Regards,
Eric