There appear to be "fashion trends" in reefkeeping as with anything else. Currently, it appears to be vogue to lean away from the large wall of rock and pursue a more minimalist look characterized by a couple of more deliberately crafted and almost "Zenlike" rock outcroppings. This is aesthetically pleasing, allows more swimming room for fish and allows for more water movement throughout the display. It does remain important to maintain sufficient rock to serve as a biological filter and of course to allow for coral placement and to provide secure getaways for the fish. So as with everything else, everything is a trade off. It comes down to personal taste balanced with husbandry considerations.