Eliminating pseudonyms would certainly have a chilling effect, and anyone who discusses the subject without acknowledging that is either a villain or a fool.

A major deterrent to candor for a great many people, in the event pseudonyms were to be abolished, would be fear that malicious polemical adversaries would tattle on them to their bosses or employers. It is all too likely that an employer who learns that a subordinate has been posting controversial opinions that the employer deems pernicious would thenceforth discriminate against that employee without disclosing the reason.

As far as pseudonymous commenting goes, giving opinions on something that someone publishes is not the same as attending a public meeting with a transcript and going on record to change public policy.   I think he misses the conversational aspect of blogging.   So much commenting isn't even directed to the person who wrote the opinion in the first place but occurs between readers.  It's the same as having a discussion about an opinion piece with an acquaintance (or even a stranger) at a restaurant, a grocery store or a ballgame - except that there is ALWAYS a written transcript of your conversation.   That's why the same people who comment under a pseudonym will show up at a meetup, tell everyone their own name, and say the same things without regard to who knows their identity.  In person, it's a conversation without a transcript.  But the idea of having a written transcript of your political (or other conversations) that can be produced at will - and used out of context - certainly drives some people to pseudonymous commenting.  

c) Section 3599.09(A)'s anonymous speech ban is not justified by Ohio's asserted interests in preventing fraudulent and libelous statements and in providing the electorate with relevant information. The claimed informational interest is plainly insufficient to support the statute's disclosure requirement, since the speaker's identity is no different from other components of a document's contents that the author is free to include or exclude, and the author's name and address add little to the reader's ability to evaluate the document in the case of a handbill written by a private citizen unknown to the reader. Moreover, the state interest in preventing fraud and libel (which Ohio vindicates by means of other, more direct prohibitions) does not justify 3599.09(A)'s extremely broad prohibition of anonymous leaflets. The statute encompasses all documents, regardless of whether they are arguably false or misleading. Although a State might somehow demonstrate that its enforcement interests justify a more limited identification requirement, Ohio has not met that burden here. Pp. 14-20.

Of course nothing here requires a site owner to accept anonymous users.

My article sought to illustrate four points:

The first is that traditional news organizations' web sites are (unfortunately) obliged to operate under stricter legal rules than 'pure-play' online forums. Many 'pure-plays' forum sites have successfully been able to claim in court that legally they are common carriers (similar to phone companies) that facilitate expression of peoples' opinions and therefore not legally liable (as in libel) for any of the opinions expressed. However, a newspaper operating an online forum can't necessarily make that claim. During the course of American history, printed newspapers have sometimes been found liable for opinions printed on in Op-Ed or Letters to the Editor pages, and many libel lawyers and libel insurance companies maintain that newspapers' online liability is no different; that newspapers' can't claim to be publishers in print but common carriers online. (I'm not advocating that's how things should be; I'm just stating that the majority of legal cases have gone that way.) So, any newspaper publisher who allows totally anonymous postings on his site is opening himself to lots of legal jeopardy.

My second point was Godwin's Law, the visible principle that says the larger the anonymous discussion, the more likely it will collapse into mudslinging and vitrol.

My third was to remind posters that just as they want publishers and site owners to be transparent against any conflicts of interest, that transparency should also work the other way. It's all too easy for people who do have conflicts of interest to post anonymously (for examples, corporate PR people posing as their products' users in citizen review sites). Just as posters should hold site owners to transparency, so too should site owners hold posters to that same standard of transparency. Nevertheless, there are cases (whistleblowers, etc.) in which a poster will need to be given some translucence.

The solution to legal liability, the effects of Godwin's Law, and the exceptional cases where translucence is needed is to understand the difference between anonymity and pseudonymity. A publisher can easily grant anyone pseudonymity providing the publisher knows who that person is, why that person wants pseudonymity, and if there is a good reason for it. The reason why the publisher needs to know the person's identity is because the publisher may also be held liable for the person's comments. These things aren't hard to do; they are regularly done in Op-Ed and Letters to the Editor in printed publications. It's the same thing as the publisher/editor/journalist granting anonymity to a confidential source. And, as Maryb2004 and Grubisich point out, there is a long history of published pseudonymity, and when responsibly done the courts tend to respect it.

Cost me a sleepless night (Yahoo sends you an Email as soon as the subpoena arrives), next morning when I looked into it, it turns out the plaintiff had cast a wide net hoping to catch a prominent hedge fund manager (which I am not, and also I didn't say anything remotely actionable, a side benefit of being a lawyer and knowing the law).

others want to hold onto that power to shut people up, rather, for people to fear enough to shut themselves up.