There's two schools of thought on this subject. One: government exists out of need. We need the government to protect us, as people, from ourselves. Two: government exists as a method of oppression, through which social elites perpetuate their dominant stature.
Arguments for both sections of thought can (and have been) made. Perhaps the greatest progenitor of the first was Hobbes, who in his book "The Leviathan", spoke about how society needs a firm guiding hand in the form of an all-powerful monarch to guide it, and to keep it on the straight and narrow. Karl Marx, of course, with the Communist Manifesto, argues that mankind can rip down the government and replace it with a perfect communist order, in which all recieve according to their needs.
What's too much? Hobbes's sovereign holds absolute power, and if you move into Machiavellian theory, he must wield this power swiftly and decisively in order to control his throne. It's safer to be feared than loved is the basis premise put forward in Machiavelli's "The Prince". Of course, we have to ask the simple question - what happens when the monarch becomes corrupt?
Well, it's fairly simple. Society as a whole becomes corrupt. In an authoritarian regime such as the one Hobbes puts forward, we have a personality cult around the monarch. This personality cult ensures that all manners of society reflect the attitudes of the monarch.
On the other hand, we have Marx's theory of communism. In communism, the elite classes are destroyed, replaced by the communual ownership of public property, on which all people live. However, in this sort of system, again, there's an opening for corruption. Communism is defined as a utopia, thus, achieving it is impossible because of inherent human flaws.
So where do we find a middle ground? Where do we find something that balances this? We find it in trial and error. Every single monarchy that has obtained power and remained a monarchy has fallen. Every single one. From the ancient empires of Egypt, India, and Rome...to the medieval nations like Alba in Scotland, the Holy Roman Empire in Germany, and the great Islam Nation that arose after Muhammed...to more recent examples, such as China, Japan, and the Ottomans...they've all fallen. This isn't coincidence. Eventually inept rulers will reign, and rot begins. This ends with disintegration, usually brought on by a period of intense warfare.
Similarly, we've never had a true communist revolution. The Soviet Union, considered the greatest attempt at communism, was a joke from day one. Marx always assumed that a communist revolution would occur in industrialized nations - Germany, France, Britain, the United States - NOT the feudalistic nation of Russia. Thus, Lenin assumed a posture of leading the people for them - not unlike the rule of the Czars - and established a ruling council, underlining the basic premise of communism, that is, rule by the working class! These elites established, as Trotsky put it, substitution. The Communist Party of the Soviet Union substituted the working class; the Polituburo (cabinet) substituted for the ruling party; the General Secretary substituted for the Polituburo. Thus Stalin takes power in 1925, thus we have, instead of an implimentation of Marxism...Hobbes's leviathan!
Do we need government? One man, John Locke, argues that yes, we do. But as government exists of need, to protect us from ourselves...it must also exist to protect the government from itself. Government must be structured to allow the input of the people, and it must be structured to keep it from becoming a tool of the social elite, or at least a tool wrenched totally from the grasp of the commoners (or the normal people, or the proletariat) by the elites.
Locke proposed a government that is seen today in most modern democracies, a government divided into three branches - legislative, executive, and judicial. Each branch is supposed to operate seperate from the other branches - ideals recognized in such documents as the Constitution of the United States of America, which was the first nation to be founded on Lockean thought.
Sadly, 200+ years later, we can see that the USA's founding document, the "great" Constitution, isn't as suited to modern life as we once thought. The American electoral system is a mess, the president wields powers he was never intended to wield, and the Supreme Court is heavily influenced by the politics of the other two branches (which quite obviously led to the appointment - not election - of George W. Bush in 2000). However, more representitive democracies like Germany and France seem to be having more success.
The fact of the matter is that the greater the power of the common people, the better government will be. Similarly, the closer people are to the government, the better government will be. One of the problems with democratic nations today is that there is too much bureaucracy - a problem highlighted in the United States. Also, there's a massive split in the influence of the elites in the American political system as there is of the working class. Let's face it. In the USA, you need an income of over a million dollars to become President. You need the support of corporations and rich elites, not the common folk. There should be donation limits, and they should be strictly enforced!
Anyway. As modern governments (many following Lockean theory, but others under Hobbesian or Marxist thoughts) pull away from their people, they lose their ability to control, to influence, and to guide. People stop looking to the government for examples, and the government itself becomes more corrupt, because people stop looking at the government. In the end, people take the examples of life around them rather than striving for more - and there's always someone corrupt to set a bad example.
Do I have a point?
Vote Kerry.