They are making a comeback, methinks. For the last twenty years, they have been predominant - but only at the side of fairways as containment!
Seriously, as Adam has said, the better player thinks they should be on the outside of the fairway or green to guard premium areas, but the middle of both should be "safe haven." And it most cases, that is probably true. If I were to use them lengthwise in a fairway, I would make the fairway wide enough on one or both sides to hold the ball in. Or make the "better" side narrower.
I have started using them more, paritally to increase surface drainage, but as long as they are there, using them to divide fairways in critical areas (especially for long hitters) or create subtle angled carry hazards in place of typical bunkers. For better players, I think fairway contour will eventually replace fairway sand hazards as the obstacle of choice for many reasons.
By the way, I call them "hammerheads."