As I've defined things above, following the Law of Conservation of Detail would technically fall in to the "hard" railroad (again, not necessarily a bad thing).
However, I often find myself not following this
Okay, so here's the situation:
When we first started the current game I'm running, I made it abundantly clear that the basic theme was a macguffin treasure hunt, and that the artifacts found would be the center point of the final showdown with the BBEG. I also made it abundantly clear that I just wanted to run a light game on which I wouldn't have to work too hard. I even provided them several pages of ancient prophecy that was to serve as their plot points. Everyone seemed to be on board.
Shortly after starting in on their adventures, they run in to the story antagonist -- a ubiquitous shadow organization/cult that is already a step ahead of them in the treasure hunt (put in simply to provide a sense of urgency on the part of the PCs). So they take it upon themselves to change the game from treasure hunt to inquisition.
I wasn't too keen on this, since the last game I ran was basically of the inquisition type (and lasted for over 2 years -- needless to say, I've had my fill of the complexities inherent in that type of game). However, I decided to indulge them for a little while, hoping that they would quickly get it out of their system. After 4-5 sessions of banging that drum, I decided to throw the treasure hunt back in their face, hoping that they would get back to following the bread crumbs ..... which they promptly ignored. I've tried several more times to steer them back on to the bread crumbs, but each time they blatantly ignore it. Their philosophy seems to be that if they eliminate the shadow organization, then they can simply go on about collecting their macguffins at their leisure without having to worry about outside threats. I've tried to dissuade them from this, doing everything short of just telling them flat out that there is no way they are ever going to achieve this before they cult themselves have all the macguffins (though I have painstakingly tried to give them that impression repeatedly).
I've even taken time to out-of-game explain to them the various reasons for various plot devices, etc; thinking that perhaps I had miscommunication my intent with the way I presented them. Still nothing.
I've even gone so far as to out-loud say that I don't want to play inquisition, but instead want to do the treasure hunt. Guess what we're still doing.
And now for how Law of Conservation of Detail comes in to play:
I work very hard to create living breathing worlds. If the players want a piece of detail, I ought to be able to give it to them, whether it is relevant to plot or not. I often describe various aspects of the world for no other reason but to instill the sense that the setting really is a real place. This also gives the players a lot of sand to move around the box. But I also make sure that the players have a clear vision of the campaign goals, and I try to make it pretty obvious what's relevant and what's not. Up until this particular game, I've never had a problem -- with the exception of those scant few that have obviously gone out of their way to intentionally derail the game for their own sick amusement, my players are pretty good a following the bread crumbs.
I"m sure I had a point I was trying to make, but it seems to be lost to A.D.D. for the moment; so I'll just stop rambling for now.