thinking about this in some depth the 1st point is this is a game set in a waste land. and really when travelling through the waste land you probably shouldn't run into half the game population. it should actual be pretty rare to bump into someone. my thought process for this is, it wont feel like fall out if there are 30 players fighting over rapidly sporming mole rats for some quest of some sort.
so how do you over come this? well i guess the world map like in FO1/2 works pretty well. but the small zones would be pretty restricting.
this i guess is where it gets tricky. i guess you could zone in on a randomly generated zone thats pretty big. maybe its generated based on the area type your in ect. then once generated by roll if other players zone in near by they have a chance in poping in on the zone you are in. if you did this you could limit the number of "random" players who could be in the one playing zone at any time.
this sort of set up would have the bonus of having a FULL ON pvp world being semi viable as there is less change that you are going to run into someone who will kill and loot you every 5 seconds. the other point is can this be sustained on a surver? (i dont know thats why i ask).
i guess it could in a similar way to wow has dungeons that people can enter separate to the rest of the world.
actual this sort of set-up would be great. by creating multiple instances of the same area or zone (even towns) if the world gets too populated it wont matter as the number of people could be semi limited. in the town situation if you wanted to find someone they could invite you to the zone they are in. this would probably reduce lag in high population zones, and trading could be done through an AH style set up. which are linked to that down or hub.
anyway that probably enough for thought. but what do people think.