A "dynamic" worldmap
I'd like to throw out there the possibility of having the world map change without specific player action.
One proposal that I've seen a few times is having "automatic" roads or paths that are created as trade between cities without a formal road-link creates it's own scar on the earth.
The caravans themselves are another example of a dynamic world.
Other ideas:
monsters/animals learn to fear humans and move away from civilization and hover around the edges
"barbarian" tribes as in the civ games that don't have their own channelers, but still fight and grow (or run out to the outskirts of civilization with the monsters)
towns growing at crossroads (if there are any)
clearcut areas emerging around cities
parties of adventurers running around
These types of changes to the worldmap would create a living world for the player to react to, and that reacts to them, rather than a dull, static landscape. I don't see this as "necessary," but if there is the time and resources to do it, I think that it would make a great addition.
Please, feel free to post other "dynamic" ideas, or a critique!