Some of the e-mail lists I'm on are, in my opinion, over-moderated, while others are under-moderated.
What happens in over-moderated lists is I join a group all new and fresh and excited that I've found like-minded people, I put a lot of thought into crafting a message, and I daydream that they will be impressed by my insightfulness, only to get a harsh slap in the face when they tactfully tell me that my contribution not only fails to be insightful, but is in fact inappropriate.
In under-moderated lists, a list may go on happily for some time, and then someone comes in and stirs up all sorts of bad feelings, driving away the people whose contributions I valued most.
Is there no middle ground? I don't think that groups (on-line or otherwise) should be a free-for-all, in which anyone can do whatever they want, no matter how destructive it is, but I also don't think that that things should be decided by authoritarian rule. I think that community members should be able to participate in deciding how the community should be run. I think that if a person's words might hurt others, rather than silence those words, let them be said, and then let the community members express their feelings if they are hurt. In that way, the community learns and grows together. That is actually how it has happened a number of times on one of the e-mail lists I'm on.
It seems to me that Quakers have a good way. Quakers believe that God speaks to all of us. In the unprogrammed branch of Quakerism, there are no designated ministers. Instead, we are all ministers. Anyone in attendance may stand and deliver a message. However, it is also expected that things will be decided by consensus within the community. If you think that God has told you one thing, but everyone else in the community thinks God has told them something different, then you all better sit down and listen to God together for a while.
A nice thing about blogs is you can say whatever you want. You don't have any moderator critiquing you. If people don't like it, they don't have to read it. Similarly, I don't have to deal with the negative people who in my opinion ruin e-mail groups -- I just ignore their blogs.
The same sort of thing applies to real life -- one aspect of getting along with people is leaving them alone. Basically, the amount of time we spend with a person should correspond to the amount of compatibility we have with them. In dealing with other people, enjoy the parts you like, and let the rest be. (There are exceptions, for example, intervening when someone is being a bully.)