it might be cool to limit such a world to certain primitives or atoms, like deformable spheres (i like to model in deformable spheres simply because i have a short attention span and i prefer to sketch than draw with detail and spheres offer that level of functionality in 3dspace to me) to see what people would do with it, and limit the kind/amount of info that would be swarmed around, let the interaction of the world be complex but the composition of the world be simple. Also, i think this would simplify the whole incremental rendering of such a world that is always swarming in in pieces, as needed.
Not sure how i would block out/off pieces in order to only download the pieces that are relevant to the user in the near-future, in order that the browser doesn't need to maintain the whole state of the whole world-- but i kinda want the whole state o the world to be maintained by all viewing it. Perhaps, the state could be partially determined/defined by the state of those swarming the world (ie. connected to pieces of it) so that it would be somewhat dynamic and immediate and have no over-all lasting existence.
Alternatively, one could view such a MMOSpace to be foamy where each user hosts their own (home) micronode and users visit and micronode-hop. I think the WorldWideFoam would be cool!!! Perhaps the ether between foam-bubbles could be the sort of dynamic-abstract space i spoke of above, but each micronode/bubble could have any kind of design limitations/esthetics/laws the creator/host chose. Again, alternatively, the rules of the bubble could be determined by the shared will of all the participants currently in the bubble...
I guess the overall goal here is to access the truly relative power of the internet as a cooperative dream. The challenge is to pull it off in such a way that mobs don't herd or stampede.. essentially intelligent/creative mobs of people creating/dreaming together.