I'm a regular reader of Eschaton, but I had a busy day, so it was something of a shock to discover this evening that he's gotten a cease-and-desist letter from some poor deluded soul who claims he's being libeled both by Atrios and by commentators on the Eschaton blog, and that half the blogs in the world have weighed in on it.
Plenty has been said about the merits, and I won't add to it. (See here for one roundup of links.)
But it might be useful to summarize some of the relevant cyber-law principles, which differ slightly from ordinary libel law. In what follows I treat the cyber-law aspects (only) of three issues: (1) Libel by a blogger; (2) libel by a commentator to a blog; (3) whether a lawsuit can force an ISP to reveal the name of an anonymous blogger.