Peter:
A sore subject w/ me. I've tried -- and failed here on GCA -- to suggest that the Principal's Nose bunker is a strategic concept, not necessarily a bunker "look" that some argue it is. To me, the genius of the original thing at The Old Course is that it's highly strategic -- go left, and you are rewarded with a less risky drive, but a tougher approach shot in. Go right of the PN, and you are faced with a much riskier drive, but are rewarded with an easier approach into the green. And, of course, all bunkers placed in or near the middle of the fairway have the strategy of driving as close to them as possible without going in them, presumably with some sort of reward for the next shot.
I can't recall how many times I've seen fairway bunkers in GCA threads that "look" like the original, but have no strategic interest, and are labeled a Principal's Nose bunker.