POL readers have much better things to do than to read a debate about the ethics of anonymous blogging. So I will be very brief in my response to Walter's critique. And I will start by reciprocating my great admiration for Walter in all things blog-related.
To me, anonymous blogging (and, more generally, other anonymous communications) are indeed justified at times. But those times involve dire consequences to the blogger. The state will kill me or imprison me if I sign this legitimate samisdat. It will blow my legitimate anonymous cover if the outlaw gang finds out who phoned the cops on them. Or, trivially, Joe's girl friend will be hurt if she finds out who wrote the helpful anonymous note telling her that her party dress is two sizes too small. I will add that the more widespread the readership and more critical the communication (blogging has a way wider readership than Joe's note to his girlfriend) the more compelling the circumstances must be to morally justify anonymity.
None of those kinds of justifications are met by the belief that one's colleagues, friends and family will be ashamed to know one's real views. Nor, in my opinion (and with great respect to my friend and former student Jon Adler) is it acceptable to try to trick tenure committees by hiding one's true views until one gets tenure. One must think little of one's law school colleagues if one believes he will be censured for the expression (and not the quality of expression) of political views. Should one stay on the faculty until "gotcha" happens? I don't think so -- that encourages misrepresentation. Confront your colleagues, or your friends, or your family, and convince them that your voice is a legitimate one.
This may be one of those areas where libertarians and conservatives disagree. For the former, no fraud or coercion is involved in anonymous blogging and that's that. [An anonymous blog posting is not necessarily itself a lie, even if the anonymity is motivated by a desire to misrepresent oneself to third parties.] For the latter, arguments are illegitimately launched when they are launched from behind a hood, as it were, unless there is a force majeure involved. We have the moral (not legal -- I'm making no argument here about legislating any of this) right to confront our virtual accusers when they confront us, I think. Ed Whelan was deprived of that right until someone (who? I have no idea, but that would be an interesting story) had enough and removed Blevins' hood.