But I could see a Fallout MMO being able to be an MMO and stay true to the setting, as well. Quite simply, the PCs could all be refugees from a Vault that was over-run/ failed/ opened successfully. In one fell swoop, you account for all the PCs starting out from pretty much the same circumstances, stay true to the setting and lore, and tie it all into the gameplay. Much like what would "realistically" happen anyway - you'd have a large mass of people that would follow a variety of paths. Some would split off and do their own thing, or even team up with the Raiders, etc. Others would try to build a Vault City (which would lead to interesting co-op between players; and the "persistent hub area that can be improved by the players" isn't really all that new of a concept, either.) Others would go off and join other factions, spend their time exploring, scavenging, whatever...