U.S. District Judge Robert Sweet in Manhattan filled 70 pages on Wednesday listing his reasons for throwing out shareholder derivative claims over Facebook’s much-maligned IPO last May. Among other things, the judge determined that the plaintiffs hadn’t gotten around the requirement that they must make a demand on Facebook’s board, and he ruled that they couldn’t show their claims were ripe by assuming the success of related litigation against the company.

But it wasn’t those findings that presumably had Facebook’s lawyers at Willkie Farr & Gallagher and Kirkland & Ellis, led by Kirkland’s Andrew Clubok, giving each other high-fives on Wednesday. In a frustratingly brief passage two-thirds of the way through Sweet’s decision, the judge also reached series of conclusions that could cast a pall over the entire IPO litigation–including the much larger securities class action portion of the case.

In the derivative cases and in the dozens of securities class actions consolidated before Judge Sweet, the plaintiffs’ core claims revolve around Facebook’s alleged failures to widely disclose internal financial forecasts that it selectively shared with certain analysts before the IPO. In considering the derivative plaintiffs’ breach of fiduciary duty claims, Sweet ruled Wednesday that Facebook "repeatedly made express and extensive warnings" to investors about the same worrisome trend that it was accused of concealing: the increased use of mobile applications among current and target Facebook users.

The judge added: "Thus, even if internal projections could be considered material to the IPO, Derivative Plaintiffs have not demonstrated that the Facebook projections would have ‘significantly altered the total mix of information in the marketplace’ considering that these disclosures were publicly disseminated." And he noted that courts around the country, following the lead of the Securities & Exchange Commission, "have uniformly agreed that ‘internal calculations and projections are not material facts that are require[d] to be disclosed’ in a registration statement."

It’s up to Kirkland’s Clubok and Willkie’s Richard Bernstein to fend off a consolidated securities claims in a complaint due at the end of the month. Bernstein declined to comment Thursday on what Sweet’s findings on Facebook’s disclosures may mean for the securities case, but he certainly wasn’t complaining. "I think it’s very important that the judge, as other courts have found and as the SEC indicated in 2005, has rejected the selective disclosure theory and thereby not overturned decades of the way IPOs are actually done," Bernstein told us.

To be clear: Facebook’s success knocking out the derivative complaints, which the plaintiffs can still re-plead, by no means ensures an easy dismissal or an anemic recovery in the securities class actions. For one thing, co-lead plaintiffs counsel at Bernstein Litowitz Berger & Grossmann and Labaton Sucharow haven’t even filed their amended complaint in the securities case. The two top-tier plaintiffs firms fought hard for the case in a particularly fierce lead counsel scrum, and they must think they have what it takes to survive dismissal. Sweet’s decision in the derivative litigation will likely prompt them to expand and hone their claims even further.

Bernstein Litowitz’s John Rizio-Hamilton declined to comment, and his partner Steven Singer wasn’t immediately available on Thursday. The plaintiffs in the derivative suits dismissed Wednesday are represented by Glacy Binkow & Goldberg; Murray Frank; Barrack, Rodos & Bacine; Robbins Arroyo; Scott + Scott; and Miami solo Scott Egleston.

Note: This story has been updated to clarify’s Kirkland’s role as lead counsel for Facebook.