First off, GREAT question/thread...
Secondly...to answer your last question...I am not a good golfer (11.6 index and been playing for 2.5 years)...and my bunker play is pretty much where my entire game is...erratic! At times, it borders on being quite good...other times it takes me multiple shots to get out of a bunker. Bear this in mind as I answer the question.
Concerning the placement of bunkers...the following are entirely and stricly my own ideas
To me bunkers and hazards in general are viewed by the golfer as a means to punish bad shots. However, I feel they should be set up to make the game (and the specific shots that involve them) more interesting. Along these lines, I feel that the bunker (hazard) should be placed where the golfer would be, at least, initially inclined to play.
If this is done then the player will have to use his mind to dream up another avenue of approach to the hole OR drum up enough intestinal fortitude to attempt a shot that "takes on" the hazard.
With this in mind and in the spirit of your thread, I like bunkers right on the green and not seperated from it. The farther from the green the more they are desigend to punish a bad shot. The more in the line of play, or right on the green, the hazards the more thrilling the required shot.
Here is a photo of one of my favorite holes and its bunker placement. Also remember the ground to the right of the green is hilly and if a miss goes there it would require a chip to a green which slopes toward the water which lies behind the green and to the left of it. Fun hole!!!