I agree that RT's picture is of a very eye pleasing bunker, but it is no more "natural" than the green or the flagstick which it defends. Bunkers are, in fact, rare in even pure links environments, and the naturall ones which do exist (you can still see some in out of play areas at Brora) have little in common with the stylized ones being built by the great designers of today, nor to the shaped and reshaped ones which might have one day been natural, but today are definitely not. Nor do "natural bunkers" happily sit in "strategic" areas relative to natural greensites, nor are they necessarily "random." Many, if not most, of the "random" bunkers on the Old Course (particularly on the outward 9) were added in the early 20th century by JL Low.
I had the chance to view the archives of one of the most venerable courses a few days ago, and when it was in primitive form (mid 1850s), there were hardly any bunkers around. Even in later, more modern incarnations, the bunkering was limited, and the Committee minutes show active ameliorative and additive bunkering programs throughout the years near the turn of the last century.
What little historical research I have done tells me that the primary consideration of early clubs and their "architects" was finding the natural green sites. After that, the tees--finding the best way to connect 18 greensites into one seamless flow. Many didn't even think of hazards until a few years after the course had been in play, and they had been identified, by experience and inductive reasoning.
To me bunkers have always been the last refuge of the architect who can't find (or create) interesting greensites and/or routings. Of course, they also look "pretty," at least to a public that has been conditioned to think that they are "natural" and essential to proper golf.
that's my Rant of the Day, but the day is very young....
PS--who was Bunker Love II, Davis' great grandpappy?
Rich