I see karma in the sense of politics. In the case of Hacker News, each person is given a vote on each of the submissions--essentially electing the best stories

I see karma in the sense of politics. In the case of Hacker News, each person is given a vote on each of the submissions--essentially electing the best stories to appear on the front page. This is a direct democracy, which has some shortcomings, particularly in voter apathy and the promotion of self-interests, where voters put their own needs before the needs of the whole. As the population of a direct democracy grows, it becomes increasingly difficult to accurately represent the will of the people (successful direct democracies usually emphasize consensus over majorities). These problems are addressed in a representative democracy, where representatives are elected to vote in place of the people, as in the case of Congress or Parliament. I believe that as online communities grow, voting systems begin to fall apart because the votes cease to represent the will of the community as a whole (the special interest groups take over the site). A common way website owners deal with this problem is by bringing in moderators or by somehow weighing votes based on some criteria, seniority or otherwise. But I digress... Karma is there to give people power over the direction of the community. Without karma, you would have no control over what you see, much like state-run media.