What is a Bunker?

Dustin Johnson missed out on a playoff in yesterday's PGA Championship after breaking a rule about not grounding his club in a bunker (see here). While Johnson was clearly not as well-versed on the local rules of the course as he should have been, my bigger question is about the particular ground rules that were used to deal with the large number of bunkers on the course.

"The dilemma," Wilson explained, "is that it's even harder to say some of these are not bunkers and some of them are, because then how do you define those? And then a player would essentially be treading on thin ice almost every time he entered a sandy area wondering where he was. And with 1,200 of them, there's no way to confirm with each player exactly where he lays."   (Link)

My problem with this explanation is that the rules that were in place do not seem as definitive to me as this suggests:

1. Bunkers: All areas of the course that were designed and built as sand bunkers will be played as bunkers (hazards), whether or not they have been raked. This will mean that many bunkers positioned outside of the ropes, as well as some areas of bunkers inside the ropes, close to the rope line, will likely include numerous footprints, heel prints and tire tracks during the play of the Championship. Such irregularities of surface are a part of the game and no free relief will be available from these conditions. (Link)

"All areas of the course that were designed and built as sand bunker will be played as bunkers …" means that someone (the golfer) has to make a determination as to whether a spot of dirt or sand was designed to be a bunker at a particular spot. If the purpose is to make the distinction obvious, wouldn't a more reasonable rule be:

"Any obvious bunker inside the lines of the course is a bunker. Any sand outside those lines should not be treated as a bunker."

Or

"Any sand on the course should be considered to be a bunker"

Given that there were people walking through a lot of the outer bunkers so they would not play similarly to an actual sand trap anyway, I like the first version better. Also, a rope is a pretty clear delineator. However, either of these rules should be clearer than the actual rule.