I never played DF, but... wouldn't his be way cooler and maybe motivate more people into learning it if it was a MMO?
More realistically there are things you can do in DF like bathe the world in lava or crack the Maximum Fun Chamber that would be kind of obnoxious for your neighbors. A bit like playing Minecraft with IC2 and accidentally leveling half your neighbor's house because your nuclear reactor melted down. Just because you are even worse off does not make people any happier about it.
And if it were an MMO then the motto could change to
Losing is fun for everyone!