Joe and Scott: Yes to both questions. At St. Andrews #7, I can see how David would have been tempted to do it, since both greens end up out on the point from different directions, and there are no traffic flow issues. But golf-wise it would be just as good without connecting the two greens.
Matt: At one point in the routing of Pacific Dunes, I wanted the third hole to play toward the 12th green site, but then later when the sequence was different I had to get the 12th hole in there. We went looking for another green site that was further "inland" and were shocked to discover the green site for the third hole, covered in gorse up in the dunes. We had to lower it a bit so that the approach shot wasn't too steep and severe ... but I found it, in part, because of my insistence on NOT building a double green.