Hussar
Legend
This linear action doesn't have to be long-term, but it does have to exist. In the beginning of the WLD, for instance, the moment you enter the dungeon the exit disappears. There is no way to detect or avoid this. That is definitely linear, it definitely usurps player control, and it is definitely a railroad. (There, Hussar, now you can have something to argue with me about.) Once inside the dungeon, teleportation spells do not work to get you outside the dungeon, but play is no longer linear. You have lots and lots of options; you do not, however, have every possible option. Some player control has been usurped, but many options abound. The railroad is over; linear play has ended; reasonable choice has resumed.
Naw, I can live with that. I would say that it isn't much different than starting any other large campaign anyway. You start out by asking the players if they are interested in something like this and go for it. Trying to surprise players with something of this magnitude is perhaps a very bad idea.

HappyElf, from what I can see, you are saying that any time a given player thinks that he's being railroaded, he is.
While I'm not usually one to side on the idea of the hyperpowered DM, I gotta call ballocks here. A player could be correct in his interpretation. But, he could also be 100% wrong. Just because he thinks he's being railroaded, doesn't make it true. There are any number of examples here of players not being railroaded, even though the DM is stripping choices away from him.
This is a definition which carries no weight. It's just like the "videogamey" term that gets tossed about. You could easily define "videogamey" as "any game element I don't like which can remotely be compared to something appearing in any video game ever". It's pointless as a criticism. If the only criteria for railroading is player supposition, then railroading has absolutely no value as a critical term.
Back to Riprock for a sec.
Nice strawman. My campaign has all of those things. But if a group of PCs has the nerve to tell one of those figures to buzz off and have the power to make it stick, I'm not about to pull something ridiculous out of my uh... hat just to make them do something.
This is not a strawman. You stated:
But having a superpowered monster, NPC or gods herding the PCs around is poor gaming in my opinion.
Every PC cleric, paladin, or druid has a god or at least divine somethingorother, herding him around. The rules are pretty clear what happens when the divine caster tells his god off. The character loses his spells for one. When a cleric violates the tenets of his ethos, he gets stripped.
Player 1: Yeah man, you should of seen it. After I snuck through the window and cut the head off the duke and duchess, I snuck into the daughters room, ravished her, set the bed on fire, grabbed the jewels and dove out the window.
Player 2: Umm, dude, aren't you a priest of Heironeous?
Player 1: Yeah, but, no worries. My DM is so scared of railroading that he thinks that herding me with my god would cramp my style. He thinks its poor gaming.
If you refuse to allow any control over your players by NPC's, how do you justify any consequences for their actions?