Pat,
Nice subject, and here is my take....
I would only do that deep, blind, bunker if it saved players from going off the golf course. Like Tim, I would tend to make it grass, unless I felt sand had a better chance of saving the shots, OR if shade or dampness prevented good grass growth.
As I have said before, I prefer bunkers to be visible, and when I do back bunkers, I put them above the green and flash them up for visibility, making them quite shallow.
Besides visibility, there is some playability theory that argues against deep back bunkers:
First, a la George Thomas, if the back is the harder recovery, you sort of encourage mild play to the short middle of the green. You have to ask if putting the pin in a challenging postion and then discouraging anyone from actually going for it makes much sense. Thomas advocated fairway beyond the green for long iron approaches, reasoning that a shot going just over the green was actually a better shot than one that comes up short. Should that be punished more harshly, philosophically speaking?
Second, four out of five tour pros I ask say that playing from a downhill bunker lie to a close pin where the green falls away is plenty tricky, since the club naturally delofts, and you aren't making a full swing. A Raynor bunker would encourage opening up the face, full swing and spin. As much harder as those bunkers look, it may be a wash as far as getting the recovery shot close to save par.
Third, as noted, back bunkers usually see far less play overall, although your argument is correct in that the type of players likely to be affected by these bunkers would be good, and agressive players. But, if put above the green and visible, they can be challenging, and contribute to the fear factor, even if only "making the course look more difficult than it plays" for average golfers.
Again, just my take. Others may disagree.
PS- What do the gorgeous space aliens have to say on this matter, and how fast is your internet connection up there?