I've gotten into a lot of Internet wars over this. There seems to be this attitude that's become more prevalent over the past few years, which says that any GM who wishes to have a plot or story arc for his campaign is a shit GM and is just railroading his players. The GM's job, according to this set of gamers, is to essentially sit there and passively react to whatever the players decide to do, adjudicating rules, rolling dice for monsters, and nothing else, for taking any more of a hand in the game than that equates to a railroad.
I had previously thought this to be an attitude amongst new gamers, reared on player empowerment mechanics like drama / action / hero / luck / fate points, but now I am noticing it in the old school community who champion so-called "sandbox" play. I find this attitude from old-schoolers, who tend to champion concepts like the megadungeon, baffling. Let's look at the megadungeon concept. A dungeon is completely scripted out in advance, unless you're using a random dungeon generator as you go (and let's face it; random dungeon generators as a general rule don't work well on the fly). Every room in the dungeon is mapped out. Wandering monster tables are set. Key rooms with monsters and treasure are placed with care and detailed. Players are deposited in the dungeon and their meaningful choices amount to not much more than up, down, left, right, forward, and backward. They can choose to sally forth or leave, parlay, flee or fight.
That's...really about it. And every one of those choices exists in a story-based game as well. A plot hook is not a railroad, because you can always choose not to follow it, in which case the GM has to come up with a new hook (and a good GM will do so, even if on the fly).
I had an Age of Conan session last month which began with the PCs waking up on a battlefield after being assaulted by a band of Picts who had come down hard, beat them in a pitched battle, and stole the caravan they were escorting. The players were met by soldiers working for the local lord (Trocero of Poitain) and whom escorted them back to Trocero. Trocero charged them to recover the caravan, and offered his resources to help them do so.
The players were not required to accept this quest. They could've said "F*** you, Count. We owe your king no allegiance and were doing this as a favor to Milo of Argos. It's not our problem," and walked away, in which case I'd have come up with a new adventure on the spot--after all, the Aquilonian Wilderness offers a lot of opportunities for play. What I was doing was offering an easy hook for further adventure, which my players chose to follow. And it led to a pretty grand excursion into a ruined lost city, where they encountered a Yig-worshipping cult of Serpent Men and Nemedian spies, ancient Lemurians, and a gigantic serpent demon (which they chose to flee rather than fight, incidentally). They did recover the treasure and were greeted as heroes upon their return to Poitain, which led to Trocero sending highest praise to King Conan II of Aquilonia and in turn led to more work for the PCs down the road.
I have in the back of my mind some major events that are going on in the Hyborian world during Conan II's reign, all in the background, but in all of which the player characters can and likely will become embroiled. This is a story, and a story of my design. Certain events in the world will unfold on a timeline because the player characters are not the only people living in the world. However, should they take a path that allows them to alter or interfere in these events, the PCs can have a major effect on how things play out. They could also choose to ally themselves with a different side than originally intended, and that's fine as well. The fact that I have an overall conspiracy going on under the surface of the world, and an organization which is working on its plan and its timeline, in no way alters or removes the power of choice from my players. I have a story in mind, but there is no railroad. At least, no more so than in any other type of dungeon or "sandbox" play. I like my worlds to live and breathe, not be stagnant with the PCs being the only ones who can ever affect change. I like my players to have the sense that there's a whole world around them, and things going on about which they may never know. It lends an air of excitement and mystery to the game...and it's my ability as a storyteller that allows me to inject that sense of life into my world.
That being said, the adventures are pretty lame without serious player involvement. That I have an outline or sequence of events in mind is meaningless without the players making vital choices which drive said events in a certain direction (almost always of the players' choosing). I've had a few adventures which were serious boners on my part and ended up being horribly and unintentionally railroady, but those are by far the exception to the rule (and I generally apologize to my players after it happens). In general, however, just having a story behind your campaign absolutely does not mean you're railroading your players or restricting their choices.
People, I think, really need to leave this "plot/story = railroad" idea behind. It's tired and in some cases, I suspect, born of people who've had shitty experiences with bad DMs (as a rule; I'm sure there are exceptions). In other cases I suspect it becomes a scapegoat sort of reaction to why people hate post-Red-Box D&D. something changed with that era that touches off a bit of distaste or rage in the current grognard community, and dozens of reasons have been put forth for why BECMI is the era in which gaming changed into "something else." I've heard Larry Elmore's art style blamed. I've heard that this version was too "Kiddified." Most people seem to agree that Dragonlance (though not a BECMI product) was a major culprit. It was too high fantasy, too epic, too (dare we say it?) Tolkien, and not enough Vance and Howard. It is from this complaint, I think, that the accusations against injecting story into the game arose. I could be wrong and am not out to speak for everyone in the old school movement--it's just that's what my observations seem to bear out.
I also think it's absolutist and representative of a style of play that I just wouldn't like. If wanting a game that has story, character development, and meaning injected into it (yes, by the DM as well as the players) means that I'm not a "true" old-schooler, then so be it. I'm not down with games where my meaningful choices involve just what weapon to use to kill the orcs, or aimlessly wandering around a world that only develops in areas where I step. It could be that I'm misunderstanding the "plot=railroad" meme, and if so I'd love to have it better explained to me. I see a lot of complaining about it, and it just doesn't resonate with me (or with any group with whom I've ever gamed). Maybe I'm saying the same thing, in a different way. I don't know. I just see a game where the DM has no story involvement as a boring, pointless game indeed. And as a long-time GM who has had far more compliments than criticisms aimed at my games, I find the idea that my enjoyment of story in my games makes me a poor GM offensive.