Thanks Tom...I'm not the historian, we've got some folks around the club who know the old stories better than I do, but I can add a little here.
The weakest stretch of Pasatiempo is the stretch of holes between 6 and 8. To be more precise, it's from the second half of 6, through 7. The tee shot on 6 is great, it's among the most interesting and strategic tee shots on the course, but after you navigate it you have the narrow stretch of fairway with OB right and trees left. The narrowness continues on 7, with the alley of trees protecting golfers on 6 and 8. The course was not designed to have trees marking the edges of the fairway...MacKenzie envisioned a wide shared fairway area for 6 and 7 that could be used by golfers on either hole without obstruction. Unfortunately, a golfer on the 8th green was killed by a tee shot from 7 tee a number of years back, and that forced the club to use trees as a safety measure. 8 is really not affected by the narrowness...it's a great downhill par 3 with the most severe green on the front nine, lots of opportunities for creativity there, it doesn't suffer from the issues of 6 and 7.
Again, I'm not an historian, but I would opine that MacKenzie's designs often failed to anticipate things that are today seen as safety issues. Perhaps more specifically, he did not anticipate that his courses would have the level of play that they enjoy in the modern era, or he did not anticipate that litigiousness would strike the golf world. Perhaps golf balls are more dangerous now due to modern equipment than they were back then. For whatever reason, MacKenzie thought nothing of routing holes with tee shots over roads (Pasatiempo #2 and #10 each originally required shots over roads, and MacKenzie was said to have shrugged his shoulders when this was pointed out, responding that the cars would simply have to wait). And he thought nothing of routing courses next to houses...his own home was built right along the stretch of #6 where errant 2nd shots must have often landed in his yard (or on his roof) with some regularity.
I'm not sure if MacKenzie was alone in this apparent shortcoming. TOC, for example, with its double greens and shared fairways, has a number of safety issues, and I'm sure other better travelled golfers than I could name other classic courses that have, by today's standards, safety issues.