I see that Tim O'Reilly has put his money where his mouth is, and come up with a proposed code of conduct for bloggers. While I don't intend to follow all the points on his list (I don't plan to get rid of anonymous comments, for instance), I applaud his efforts. Out of the entire list, this stands out as the most important:
We won't say anything online that we wouldn't say in person.
The rest, as they say, is commentary.