Mark:
I agree with Tom Doak that the existence of "greens within a green" has been around a long time.
Certainly NGLA is an example. I doubt that term was ever actually used back then though (I think that actual term was started on GOLFCLUBATLAS.com) and perhaps even the concept wasn't recognized so much back then simply because a lot of the actual function or effect of "greens within a green" has to do with green speed.
For instance, if NGLA runs their greens at or over about 9.5-10 on the stimpmeter #1, #3, #6, perhaps #11, #12 and #14 have legitimate pinnable positions where a ball coming from various other parts of those greens probably will not stop near the pin in those otherwise legitimate pinnable areas.
That to me is basically the definition of the concept of "greens within a green".
The pros of that concept is it can and does become highly strategic (generallly for good golfers approaching those greens) but the cons are a good many golfers look upon this concept as unfair as they seem to believe that a golfer should have the opportunity to reasonably two putt from anywhere on a putting green even if it's somewhat intense. The feeling is it needs to be possible and the same attitude seems to be true regarding recovering to any pin from around a green.