I haven't fully thought this out, but just a trial balloon stream of conciousness to see if this makes any sense...
Anything that effects the progress of the ball's intended result of playing the next shot or into the hole is a potential hazard on the golf course. Anything that is desired to be avoided 'while the ball is in motion' is a hazard. ONce the ball is at rest, it becomes a challenge or condition of play. If it is resting in a pond, it becomes a next shot challenge or condition. Only when the ball is in motion and there is a potential for an unfavorable result to come to rest within or upon, is the pond or bunker or waste a hazard. A small stone that effects the desired course of a putt or chip, is a hazard of impediment while the ball is rolling. The carry of the ball by wind to an undesired location is a hazard of wind.
The other tact of identifying a hazard as noted above is the hazard of mentality or psychology. Those are the situational things that happen before the shot is made. The tee box right next to the members dining room, the green next to the club house where everyone is watching as the golfers finish. The audience of your 4some or observers where you allow some form of peer or playing pressure or anxiety to effect execution. Could that huge amphitheater at the Phoenix par 3 where thousands are watching and cheering be a hazard of psychology? Could the tee box anxiety, as noted above, of a longly anticipated famous shot on a legendary course be a hazard of sorts?
But, I love John Kirk's ideas, no matter if it is explaining a hazard, or just offering a measure of golf's ultimate excitement and great design. The longer time span the player is focused on execution and result, the greater the design. When the tour players hit their tee shot, and don't even bother to look where it went, that is rote, unexciting and uninspiring design. When they follow it with anxiety in there eyes, even when they hit is solid, and watch it all the way to the result, or don't see the result, but stare and wonder, that is excitement. I loved playing BallyNeal when shots were hit that felt good, but the whole group watches intently to see or not see the result, with Adam calling, "show your face" to the ball that goes out of sight on undulating FW or near a green platform.
The ball in motion and how it got there is the game. Whatever is undesired and can effect the result while in motion is the hazard.