What happened to my sister in law, was in an MMO, a computer moderated shared fantasy world. Although shared is a big word here, as it seems. Players can shout at one another, but the group effort was suddenly gone. Not so shared in this case. That was a change from before. Then you could always help eachother.
But before, though you could help eachother, the world never really changed. You could rescue a town as many times as you liked, because it would be threatened by the same monster again and again. Like trolls from a freezer, monsters and enemies were respawned everywhere. Maybe then the world was sort of shared, but you couldn't really change it.
C'mon, real sharing can't be that hard?
So why don't the programmers allow you to let one person win the quest, and let the others have bad luck, and have em rescue someone else? That's what they try in some other MMOs, my brother tells me. But the problem is, that people pay to play in an MMO, so they won't be pleased if there is nothing left to do because someone else was there first. So even in this other MMO, the evils do respawn, after a longer while.
That's the problem with shared worlds, preprogrammed ones at least. It seems to be very hard to really share them, and have a unique gaming experience for all players at the same time. So in practice you may end up playing alone, and just meeting in the lobby. Or you play in a world where you don't make a difference even if you are umpteenth level, because everything trollspawns after dying – including you yourself.
I don't know, but it looks like MMOs are in need of an other way of generating stories and quests. At least to capture my attention or limited spare time. Which may be possible. Just have to figure a way how.
How about Tabletop Sharing Games?
Most tabletoppers don't share their games with other Game Masters. With Dark Dungeon we did do so, for about fifteen years. Eventually we scattered again as core GMs got into real jobs or emigrated across the ponds. We didn't have paying customers, we didn't have quests everybody needed to do (although we tried), and we didn't have respawning monsters. But we did have similar problems.
Sharing the world and allow players to change the world - or even let all GMs change the world turned out to be scary. Most GMs didn't care to do world-shattering stuff. But those who did seemed to be unable to communicate or compromise on what would happen. Most of the time it went well enough (I guess I just overruled some of them), but at one point the older players became really frustrated. And that was because the younger players spawned all sorts of horrible creatures, armies and treasures where the older players had already saved and solved the world and wanted... well, to be seen as heroes. They didn't want a new spawn of monsters for a new groups. Or at least they wanted the same respect from the new players as they figured they had fought for in the old groups. And the new groups, they wanted respect too. That was less easy than it sounds.
So, sharing is something we seem to seek out. But also something that's hard to do.