Mark:
My local nine-hole muni put in two of these a few years ago, and they are the single dumbest things I can ever recall seeing on a golf course, and I've seen plenty of waterfalls. A strip of rough, 15-20 yards deep (to prevent balls from running/bounding through), across the entire width of the fairway, at the exact landing area for even hacks like me (and I'd wager the average handicap of this course is upwards of 20). And they are on holes with no real strategic options to avoid them -- either purposely hit short of them, or try to fly it, or settle for a good straight drive that ends up in rough.
(One of them is really particularly dumb, because the hole -- a sharply doglegging par 4 -- has some decent strategic merit, at least for a muni -- OB left for a really pulled tee shot, trees bordering the OB, a sizable trap with a high lip at the crook of the dogleg, with some of the longest rough on the course fronting and behind the trap. If you want to avoid the trap and the trouble around it, just aim right -- but that lengthens your second shot -- an uphill one at that -- into a green with a fair degree of slope framed with traps left and right. IT'S A DECENT HOLE, for a muni. With a stupd strip of rough sitting in the middle of the fairway.