It is incredibly fascinating to think that with the right magic item or cosmic occurrence the party could skip to another DM's world. It's a shame that when the idea of the Multiverse was bandied about regularly the internet was not in wide public use. It's even more shameful that groups don't share their worlds and the varied stories of their experiences in those worlds. There's this great absence of a community of gaming creativity that should not be.
I'd love to have the time or resources to try and network the creations of various DM's and encourage the sharing of adventure stories. Just hearing about how Group A reacted to the setting created by the DM of Group B and vice versa would be entertaining by itself. There very well could be small collectives of groups doing this, but on a greater, worldwide scale it would be all the more marvelous.
This is a dream of mine that I would love to see made a reality. As a hobbyist it gets at me that I alone can't make this possible. Not right now at least.