This is fascinating stuff. I wasn't particularly familiar with the concept before reading the shades of grey link.
It seems that a number of the more "serious" micronations are grounded in the concept that the territorial nation-state is becoming a anachronism and that people should be able to choose their citizenship status irrespective of geography. It's an interesting concept, but I think we're a long way from it establishing any grounded reality.
Too many of the functions providing by the territorial state and its subordinate local divisions are geography dependent. Nation-states impose laws in order to create physical living conditions amenable to the citizenry's values. It seems to me that some new structure or institution will have to be created to serve those functions.
Additionally, the role and value of a "micronation" will have to become a lot clearer. How does a worldwide political union of like-minded individuals create and execute policies that result in real-world, tangible lifestyle benefits for its citizenry? If it doesn't, if that's not its goal, then what is its goal, and what's my motivation for belonging to any nation?
Carl