In my post below on the autoadmit case, I noted that the pseudonymous posters faced huge professional risks from being identified. But say that one of them decides to fight the case to trial (unlikely, but assume he does).
In a typical libel case, the plaintiff may worry that filing the case, and having a trial, will only further spread the libelous accusations. Even if the accusations are ultimately disproved, more people will have heard them, and some may pay more attention to the accusations than the ultimate disproof. This isn't really an issue here, I suspect; I doubt that anyone will really believe that plaintiffs really do have sexually transmitted diseases, for instance.
But libel cases also let defendants discover many things that plaintiffs might find embarrassing. Consider, for instance, Doe I's claim that the "harassing, offensive, and false statements posted by defendants" caused her to get no job offers through the on-campus interview process, even though she had sixteen on-campus interviews and four callbacks (paragraphs 30-33 of the complaint). I'm skeptical that there was any causation here; as Ilya pointed out,
First, most people know that anonymous comments on chat sites are often inaccurate, and intelligent employers are unlikely to give them great credence — especially if doing so leads them to pass up a strong job applicant from what is arguably the nation's most elite law school. Second, even if law firm hiring committees did believe the comments, ... [m]ost big law firms care very little about associates' personal lives outside the office, so long as those associates are racking up the billable hours. Even if one or two firms were deterred from making offers to this student by the internet comments, it is highly unlikely that all sixteen (or even a large percentage of them) were.
Instead, it seems to me that the likely reasons for Doe I's striking out were among the normal reasons why many people who look great on paper don't do as well in the hiring market as they'd like — they don't seem that interested in firm jobs, their credentials aren't really that good, they come across as too quiet or nervous, they come across as too brash and self-important, they flub some questions, they rub the interviewers the wrong way, some of their professors are unimpressed by them and say so, and so on.
But even if I'm wrong, surely defendants would be entitled to try to prove that there was no causation here, given that plaintiffs are making an issue out of this (an issue that bears directly on actual damages, and indirectly on presumed and punitive damages). Presumably defendants would subpoena the firms involved and ask them why they didn't hire Doe I. (I don't see any reason why such an obviously relevant matter would be found undiscoverable or inadmissible.)
Even if I'm wrong and the firms were somehow influenced by the online nastiness, I expect that their hiring people would do anything short of outright perjury to minimize that and to maximize the conventional reasons why they thought Doe I was unsuitable. If I'm right, or at least right as to many firms, those firms would quite candidly explain why they thought Doe I was unsuitable. Some of them may be politic ("we had an exceptionally strong pool that year, and she just wasn't quite as fantastic as the other Yale applicants"), but others may not be. (Remember that while many firms are reluctant to say anything bad about an ex-employee, for fear of a libel lawsuit, witnesses are immune from libel lawsuits for their testimony.)
So the result will be testimony from sixteen prominent law firms explaining why they didn't want to hire Doe I. What's more, the law firms aren't being painted as the bad guys in this law suit, so it's not a case where (for instance) someone sues an employer for discrimination and the employer's badmouthing of the plaintiff could be put off to the employer's racism or sexism or what have you. It's just sixteen law firms that come across as largely disinterested bystanders (despite the possible reason to shade the truth that I mention above, a reason that is likely not to be prominent in observers' mind) and that talk about how Doe I botched her interview, or about how her grades were really pretty weak. That's not exactly the best publicity for an aspiring young lawyer, especially given that the case about online chatter is likely to lead to online chatter.
Again, perhaps all this is moot because there's virtually no chance that this case will get to trial or even to discovery. Still, it's the sort of thing that libel plaintiffs ought to worry about in similar cases, and perhaps even in this one.
UPDATE: Ann Althouse has more thoughts on this, and the AutoAdmit controversy more broadly. Plus, one of the great things about Ann is that she mixes highly accessible posts about interesting legal controversies with asides about pretty technical but important legal questions, such as federal court jurisdiction — she has some thoughts about that in the second post. (Recall that she's a jurisdiction, federalism, and constitutional law scholar.)