The experiment lasted long, but was eventually overruned by Roman Empire troops. Ironically, Rome had, in previous centuries, abandoned monarchy, expelled the king, and started something very simillar to the greek system of governance. Sometime before conquering Greece, it had already turned into an Empire (that is, a republic dominated and ruled by the Army's Commander-in-Chiefe, the Imperator).
Not much changed on this realm with the fall of the western empire and the dawn of the medieval age. Sovereignty was a right of the supreme ruler, who might delegate it to local land barons, but who eventually claimed it all back with the help of the new sprawling commercial centers in the late XIV century and onwards.
It was only in the XVII and XVIII centuries, with the tentative revolution in England, the independence of the United States of America and the French revolution that the greek experiment was revived. This time, it had much broader scope: in principle, any free man could vote. That was the case in Greece to, the perk was the definition of free man: they amounted to about a third of the population of ancient greece. Free meant both native and wealthy: those without income must subject to capital holders. Wages were not high nor reliable, so you either had a lot of (social, monetary, land, political) capital or you were kind of a slave.
Then came universal suffrage. All men and women, no matter their social position, level of education, could vote, as long as they were of age and could draw their own name (literacy has pretty loose definitions, at least in Brazil).
Sovereignty, as defined by the Brazilian constitution, comes from the consent of the people. Even if it has to be presumed (Anyone want to question my authority? - said with a menacing stick in hand - Anyone? Good, we agree on this one... Now, about that speech freedom thing...).
This bit of history gets me wondering. What will come next? Some people believe in the dissolution of the State-Nation, with the rise of organizational citizenship and sovereignty. Meaning we will either be part of a powerful transnational organization or be excluded. I can see some moves in that direction. While the most powerful organizations are national governments, with all that legitimacy, law-making and police enforcement, taxes and what not, and the sovereignty over the nations's land, its business as usual. Watch out for any challenges on those monopolies in the near future.
Anyone remeber the governance regime for colonial India under the Eastern India Company?