Stone Dog said:
Unfortunately a lot of the campaign setting doesn't touch on this. I've had this argument before and I have to admit, despite how easily you could focus on this aspect without changing the setting, the actual ECS book describes the Five Nations as being largely pretty secure. Your Eberron may vary as mine certainly does, but it isn't an unreasonable disconnect.
Depends on what you mean by "Secure".
Take a look at the maps. Unless the red dot goes through an area, there's no lightning rail. That means there are only two real ways of communication between "Points of Light": Orien mail services and Speaking Stone stations. Your little hamlet out there may not have a Sivis Enclave big enough to warrant a speaking stone. Sort've like how you can live in a town in the US not big enough to warrant a redlight or a McDonalds.
So with that said, take a look at the map of say, Breland. While the whole South of Breland has a lot of populated areas, North and North East are very sparse. The Northeast is especially dangerous, given its proximity to Droaam.
If you're anywhere in the Northish areas, and no where near the lightning rail station, you are boned. That's a lot of room for darkness. A lot of disconnect from the south of Breland.
Another thing to keep in mind is that the Mournland is smack dab in the middle of Khorvaire, so countryside that was once peaceful and had no monsters now has monsters just strolling out of the Mournland in all directions. So you have the edges of all the nations around the Mournland with a new influx of beasties.
Also, something that must be realized is that Eberron doesn't just have points of light, but there are points of darkness IN the light. You have cultists worshiping the fiend bound in the Silver Flame in Flamekeep/Thrane. You have Quori infiltrating Sharn, Q'Barra and many other cities. The Emerald Claw is a terrorist organization that could attack in any city. Incursions from Khyber could happen in the countryside or in your back yard. Cults of the Dragon Below could infiltrate the city, made up of the nobles or the guildhall down the street. The Swords of Liberty, a terrorist organization in Breland, want to overthrow the king and institute a Democracy - which would severely de-stabilize Breland, if not the Five Nations.
I see Eberron like the night sky. Sure, you have groups of light points around constellations, but you still have lots of void, and lots of isolated points.