So, interestingly enough, yesterday's blog entry inspired another question from a different reader. In a game they were running they had performed a GM fiat, and wanted to know if that was too rail-roady because they didn't want their game to be one. Like quite a few GMs I know, they seem to be afraid of their game coming across as a railroad, which while sharing in the condition I also find to be an interesting response.
Before going into how they are different, I should probably define the two terms - at least how I see them - for the argument. For railroading I think this is the second or third time I've defined it, and I don't think I've ever defined it the same way twice, so bear with me. (Is that the right bear?)
GM Fiat: A GM Fiat is an instance where the GM waves their hands and just makes something happen. It can be used in the party's favor ("you cross the ocean with no problems what so ever"), or against them ("he gets away"). It is, in essence, the GM making something happen in such a way that die rolls are negated or just not used.
Railroading: Is when the GM removes the options from the player. events happen with little or no effect or impact from the players regardless of whether or not the players should be able to have impact on them. Railroading, even while sometimes it can work out well for the players, is something I feel should always be avoided as it is narrowing the scope of the game to the point you can only go one direction. It makes it so that players are essentially along for the ride, not playing a game.
So what is the difference? In essence the only difference is how much it is happening. A GM Fiat is an isolated matter, the GM makes one thing happen but otherwise the players have significantly more control over events and how they happen. Railroading on the other hand, is essentially constant fiating. Railroading can happen without fiat, such as with God NPCs and other means of making sure things always go one way and one way only, but in essence a Railroad is a constant and consistent trail of Fiat that removes the power from the players hands, while a Fiat is a tool to briefly make something happen but otherwise leave power with the player.
Personally, I think Fiating is fine. I agree with the sentiment put forth in books like Mutants and Masterminds that sometimes a Fiat is necessary. It lets you protect important plot points at times, it lets you build a recurring villain or antagonist to really help the party with getting into wanting to finally beat them. It can do a lot of good, however I also agree that when you perform a fiat you should pay the players. Mutants and Masterminds does this by allowing the GM to fiat (explicitly stated in the rules) provided that those characters directly effected by the fiat in a negative way get a hero point.
That being said, you need to be careful when using a fiat. Try not to whenever you can, try to do it 'by the rules' as much as possible. Use your fiats sparingly, and when they do happen they are more likely to just be glossed over rather than stand out. If you keep having to save a certain NPC with fiats, maybe you should just let the NPC go, or use them better. After all, your players will catch on that you are protecting that NPC, it will stick out that you are doing so and quickly becomes "The GM won't let me catch/kill that guy" instead of "Gah! He got away again!"
You especially want to be careful with fiating because, as said above, once you start using it often your game becomes more and more of a railroad. You take away more and more choices from the players and more narrowly define how the game can go.
These are things to watch out for, but at the same time that doesn't mean to shy away from fiating either when it is necessary. In fact, there are even good times for using fiating. Granted you need to put some thought in and be subtle about it, but introductions for new and major NPCs are a great time to use fiating. Have them come in, do something, and get away. If they need help, use a fiat quietly to do it. First impressions are huge, and if you want an NPC to come across as bad-ass you don't really want to trust something as random as a die for their introduction. Afterwards you can use dice and say they rolled badly, but that initial impression just go for it.
Another thing to remember about fiating is that you shouldn't use them to directly hurt a PC. You can use them to hit a PC, but don't have a fiat'ed blow do much, if any damage. Not much sucks worse than being removed from a fight just because the GM arbitrarily decided you were going to be hit and then rolled incredibly well on damage.
Finally, remember that you can use Fiats to help, and you probably should if you have been using them more lately to hinder player desires. If you used a fiat a few times to help someone escape the players, next time the player is doing something important but not necessarily vital just wave it through. Be fair with the fiating, if nothing else it gets through that when you do it you are doing it for the story, and not out of some competitive GM vs. PC desire.
Looking back on this it became more about how to use GM Fiat instead of the difference in Fiating and railroading. Then again, the differences are pretty small but important. As I said, a fiat makes something happen (good or bad) in an isolated manner. Railroading is the constant and consistent removal of power and choice from the hands of the players, making them more into spectators than participants in the events that are unfolding. Fiating can lead to Railroading, but they are not the same thing, and fiating is a useful tool to have in your arsenal for those times when you really need it.
Hope this helps, though I've probably just caused more confusion. That being said, if you have a question on something I've written, feel free to drop a line at firstname.lastname@example.org