This isn't just about blogs. It's also about mailing lists, newsgroups, forums, IRC channels, anywhere where people hang out and exchange their views. (And yes I'm implying parallels in the "real world" too. This issue is hardly new. Just look at some pamphlets from the 17th and 18th centuries.)
I think that Boston recently witnessed an instructive answer to net nastiness, when Kerry Healey, the recent Republican candidate for governor, was disinvited to the advisory board of the American Repertory Theater .
During a contentious March 19 meeting to consider Healey's appointment, several members of the ART's 40-member board criticized the Republican nominee's unsuccessful campaign last fall, calling it mean-spirited and condemning a controversial television ad that highlighted Deval Patrick's advocacy for a convicted rapist.
The point here is not that she lost the election, but the way she lost it — and the sense that Rove-ian nastiness should carry consequences.
On the Web, you should be free to be nasty — and willing to accept the opprobrium that nastiness calls down on you.