Questions on Democracy

Hi, to my Social Advocacy Group, please post all your questions on Democracy for our Social Studies essay assignment. We always regard democracy as the best form of government for any country. Does democracy really lead to stability? If we were to examine human nature, is there really such a thing as an ideal form of government? If there is, is it democracy?
Remember that we must define democracy. Theoretically speaking, there are many types of democracy. In the real world, there are even more forms of democracy, with some countries following the political ideology closer than others. Although it would be easier to focus on democracy theoretically, we must remember that the essay that we are writing is on Social Studies and thus, we have to constantly bring in examples of democratic nations around the world.
In a democratic society, people get to influence the decisions made by the government. They can do this by voting for a policy or electing a representative into the government. The assumption made in this political ideology is that people know how to make the right choices. I feel that we should question this assumption. Isn't there the danger of the Bandwagon fallacy in democracy (where one person makes a certain decision because the rest are doing so)? Do people really know how to make the right choices? A scientist (I can't remember who, sorry) once published a report claiming that humans are naturally selfish. So in a democratic society, although the ideal situation would be that everybody wants to achieve a common good for society, is that really the case? Or does everyone just vote for what they want?
Let's examine this logical flow - if humans are naturally selfish, that goes to say that people will vote for what they want and advocate what they want. Since there are always conflicts in the viewpoints and ideas that different people have, that means that people want different things. If people want different things for their satisfaction, is there really such a thing as a common good for the society? Who determines this "common good"?
Of course, to ensure that ideas that are outrightly detrimental to the society are not carried out, the government has to intervene. The government always promises to listen to the people and not necessarily grant them whatever they want. Thus, in any democracy, there will be instances when the government makes decisions that go against what the majority wants because it feels that that is the right thing to do. How often can a government do this without arousing anger in the people? Does the government always know when to make the right choice?
OK, these are some of the questions that I brainstormed. Perhaps you might want to pick some of them up and discuss them in the Comments section.
Thanks
Kirk