Tony,
That was "The Holy Grail" that used coconuts...Patsy in particular.
But to Don's question: It comes down to a business question, really. When doing golf(design/ building/ remodeling/ operating) it all comes down to giving the customer what they want. Here in America, it has been a matter of aesthetics for a long time. While this fanatic group of golfers on GCA.com seems OK with polystands(at least with their online stated preferences), the general public most often prefer the monostand grassing methods. The golf course with pure bentgrass fairways and pure bluegrass roughs is certainly striking visually, but does it make the golf experience any better? Maybe so, if aesthetics are higher up the list than most would admit to, and certainly in this crowd.
The thing that happens with a polyculture(as Don is describing it) is that the plants that remain over time are sustainable...they've survived whatever the maintenance regime has encouraged. Survival of the fittest doesn't mean the original grasses survive always, but possibly subspecies of those plants, or even other grasses from other means is what remains. When maintaining a turf stand to keep it "pure" the maintenance is driven by those stands. Superintendents have a plethora of tools, and may stop at nothing to use them in order to keep those "pure" stands intact....after all, that's what was planted when the course was built, it must be what the original architect and superintendent had in mind, right?
I don't know, Don. Sustainability is a strange word in golf, because by very nature golf isn't really sustainable due to the huge amount of maintenance practices required. But, sustainability ought to be a principal by which golf (and all of us) operate....it's just a better way to go and almost always cheaper in the long run.
Joe