While some of the individual sites are great, and some of the information on the technical sites are terrific; it is the more opinion-based sites which I have had a problem with.
I've found twice now (narrow sampling, but one with the depth of years of participation and thousands of posts) that the nonprofessional nature of the moderators tend to lead to abuse of power. It's an inherent problem with the democratic nature of the Stack Exchange network, as opposed to having more dispassionate professional moderators (or at least a professional moderator oversight) which would be more like a republic to my mind.
A democracy, after all, killed Socrates. Plato, Socrates' student, invented the republic to grant individual rights even against a majority. To protect individuals against the tyranny of the majority.
Now having said all that, fine it's understandable. Businesses are interested in making money. Hiring impartial moderators from outside a community perhaps benefits such a small minority of individuals that it doesn't make business sense. Fine, that's perfectly reasonable.
Which brings me to my larger problem. Once an individual has decided they are no longer interested in participating on a site, Stack Exchange mandates that all their posts remain. The individual has no recourse. Stack Exchange claims this right under "fair use".
I would suggest that, when someone leaves a board and deletes their account, it deletes all references to themselves on the board; they should be permitted to remove their posts/ideas with them.
Fair use, permits limited, sited use, not indefinite anonymous use. If the account has thousands of posts and tens of thousands of votes, the author should still be permitted to delete his posts with his account. While deleting such content, potentially diminishes the site, I would argue permitting the content to stay over the objections of the author is worse.
The diversity of opinion on the site is gone with the author. Deleting one's account in which much time and effort is a statement. By retaining the posts Stack Exchange has taken away, the last voice the author had to express themselves; silence.