You know, the problem with Slashdot's moderation system is that exactly half of all users are idiots. If the balance was tipped even a bit, the moderation system would soon make the dominant group of users the one that has the most karma and moderation power (not only because of groupthink, but also because idiots usually agree more with idiots and non-idiots with non-idiots than idiots with non-idiots and non-idiots with idiots). The only possible reason for that one can see both idiots and non-idiots posting on Slashdot with high amounts of karma is that there are exactly as many idiots as non-idiots. IOW, each time an idiot loses a substantial amount of karma, a new idiot will register and immediately start gaining karma, or perhaps a non-idiot will get modded down.
I intend to call this rule the Rahikkala's Universal Law of Mass Idiocy as soon as I've made the necessary changes to generalise it to apply to the universe at large.