there isn't a limited amount of land that everyone's vying for and if someone wasn't online, you'd really never know they were there at all. For all intents and purposes, a players' kingdom does not exist (to other players) unless you already know that it's there--we don't share borders on a giant grid like some games approach it ... If you look at screenshots of the current World Map, you'll see that displaying every player's city really just isn't a feasible goal for DoF, or any game that I can think of.
I agree that it's not a feasible goal [for many players to be on one map with such density that borders are increasingly tight]; with that said, I was working from the assumption that DoF would not be taking the EVE Online approach with one massive server for all, and would instead go with an even smaller traditional shard approach. With these shards in mind, though, I suppose I must raise an objection to the idea that many players will likely never run into another, even if on the same server, simply due to the game map restrictions on space. Now, obviously there are technical limitations to consider - but this is where the MMO aspect comes into friction with the RTS.
Consider the current model, minus the MMO aspect:
We have a relatively large game world with various campaigns (with various lengths), quests, etc... a great new spin on grand RTS. You have your neutral cities, AI enemies, and yourself. Divide, conquer, etc. BfME2 meets Total War. Certainly not bad.
Add basic multiplayer functionality:
Now we've expanded the possibilities of the above: we already have skirmish mode with 4-6 players (I understand this is still under debate). Great. Now, what of the larger-scale war mode such as the current MMO parts? Now we have a great LAN party. With the player world only so large, though, what kind of numbers per-map, and then maps-per server (assuming servers are region based and not map based) can we come to expect for maximum player interaction and server stability?
Add MMO component:
For a truly "Massive" multiplayer experience, I imagine at least several hundreds/several thousand players in a server. With the restrictions on the game map - let's say... for argument, a couple hundred players. By a typical MMO distinction, this seems like a pretty small amount per server. It might be the only manageable number, which is what I think your post was explaining, but it's still rather small.
I'm just guessing as to the player number per server, but I can't imagine - given the limited space in the game world, and without making things crowded - that the game will have that "massive" feel as far as the gaming population per server - but will instead come out more in the large-scale RTS side, ala Total War - just with multiplayer support. The 'massive' component then coming from the battles, strategy, etc. The traditional MMO mechanic of many people, then - would either be lost or, as your post explains, buried unless you know people - or however it is decided that you would interact with random MMO players.
If a dev could comment on the technical side of this, I think that would help. :P