The web doesn't open any new possibility in that respect. There are MMOs where the visuals are centrally served. The client keeps a cache that is often updated

The web doesn't open any new possibility in that respect. There are MMOs where the visuals are centrally served. The client keeps a cache that is often updated from the server side. Really, this has never been a significant problem to stop studios from letting you mess with their worlds. There are other technical problems related to world representation, but most importantly, there are design integrity concerns. To design a world that the players can meaningfully modify but not screw up completely in various ways (mainly related to theme, playability and balance) sounds like a difficult, laborious task. If you're interested in this kind of stuff check out what this crazy swede is doing: http://www.quelsolaar.com/ http://www.quelsolaar.com/