This has got to be one of the trickier problems for a designer. IMHO the bunkering should be used for more than just one function. Granted the primary opinion is limited to the afore mentioned 'protect the A postion' theory. However, I feel that they should have more functions. They should be used also to create drama, accentuate the aesthetics and in some cases even save the golfer from a worse fate.
The problem with placement for the everyday player is that the range of ability varies greatly. The use of multiple tees (to help make the club selection relatively consistent) can palce the forward tee and Pro tee palyers in the same landing zone and the rest of the spectrum a bit behind them. So, if you bunker strickly for the Pro, you tend to put the weaker players in the same jepordy.
When looking at a venue like Torrey Pines South that is marketed as a Championship Venue, it can get awaywith focusing primarily on the game the Tour Pros play especially when they have multiple courses - Medina #3 is the same, they have other courses for the rest of the memebers to play. Same with Oakland Hills, Cog Hill #4, Bethpage Black, Olympia Fields, LA CC, etc. This gives them the flexibility to stratify the play to different courses depending on ability/enjoyment.
The problem comes when you try to make one course 'all things' to all players'.
As for bunker styles, hopefully the fit in harmony with their surroundings. A rugged site calls for rugged bunkers. However, putting rugged bunkers in a parkland setting might make them appear to be just 'unkempt'. To me, the stacked sod bunkers of Scotland are at odds with the natural setting - too formal. Especially if you go back and look at photos from the early days, before they 'cleaned them up'.
So how does one ger around all this? I like to obscure the cookbook, formulated placement of fairway bunkers with a more random look along the line of charm. Granted, this isn't the most economical solution but one the works for me. Besides, bunkers aren't really hazards for the Pros anyway, 6" of long grass in-leau of sand would be much more hazardous to their scorecard.