Ken,
This is a very interesting topic. I recently wrote an article that appears in the July 2011 issue of Golf Course Architecture magazine discussing this very subject relative to Dr. Mackenzie's original design at Augusta. If interested, the article's here:
http://www.mingaygolf.com/Bunker_Blitz_at_Augusta.pdfAs I state in the article, I think in many cases bunker have been, and are overused. And, like you, I've often thought about whether or not bunkers are in fact forced into the design of golf courses on a non-sandy sites. As you know, because golf was born on those sandy coastal properties in the UK, where bunkers exist naturally and were incorporated into the design of nearly all links, they have become traditional features and certainly make the game more interesting, and courses more attractive than otherwise in many instances - even where sand does not exist naturally.
I do think a world-class golf course can be built without sand bunkers. Obviously, the key is contouring through the green. With enough interesting contour, complimented by bouncy turf (and wind), bunkers aren't necessary for interesting golf. But, as others have stated, would a course without bunkers be accepted by the golfing public at-large... no matter how good? And, how many developers would agree to allow a course architect design/build a course without these traditional features?
With enough money in our pockets, and an interesting property to work with I know a few designers, including myself, who would like to try to create a top-notch course sans bunkers.