I'm "Paceman" as referenced in the above article referral by Jason, and to tell the truth, almost all of you are correct when it comes to the causes you are listing for Slow Play. Literally there are thousands of reasons, but through my research I've broken them down into five manageable categories: 1. Management Practices, 2. Player Behavior, 3. Player Ability, 4. Course Maintenance Practices and set up, and 5. Course design.
I've worked with courses in the U.S., Canada, Hong Kong, Singapore, Scotland (The Old Course and the 2002 Open Championship at Muirfield) and Ireland and shown them that in order to successfully manage the problem of slow play, you have to treat both sides of the equation - the side for which management is responsible and the side for which the players are responsible. Focusing only on one of these will never provide a lasting solution.
Now, when it comes to this thread on architecture and the pace of play, Bobby Weed is right. No matter what the design, the architect determines the time it "should take" to play the course. Because the architect determines the playing length of each hole, the location and difficulty of obstacles, the distances traveled from greens to tees, and the sequencing of holes which plays a huge role in how smoothly the course plays as many of you have already pointed out. In fact, I work directly with architects and owners to advise them during the design phase not only on how long it will take to play the course that is under design, but where and how long the bottlenecks will be under different starting intervals and how management can optimize revenue and by properly loading the course and monitoring the pace of play once it's opened. I recently assisted the St Andrews Links Trust in helping them decide between two of David Kidd's routing options for Course #7.
Slow Play is a problem that sounds both extremely simple to understand and at the same time very complex. Couple that with the fact that many of the solutions are counterintuitive and fly in the face of common sense and it's no wonder it has been such a difficult problem to solve.