There's a term in Russian "синдром вахтёра" which I think should be translated as "a doorkeeper/janitor syndrome". It's a phenomena when a not very smart person who doesn't understand the big picture of things gains a little bit of power against his fellow mates. While generally not intending to bring a harm, they begin to implement some weird but strict policies that reflects their very poor understanding of how things should work (metaphorically they think that every line should either be parallel or perpendicular to each other and no deviations should ever exist). Given that at least some of them might just enjoy having and exercising that little bit of power they have, the result could be just ugly and destructive.
Unfortunately, in many cases I've ever seen over the Internet communities (that's not to stretch the idea further), those who want to become a moderator are very prone to this syndrome.
I think to create a healthy community some extra special measures should be implemented to prevent this phenomena. Unfortunately StackOverflow is not doing it enough (if doing anything at all).