The withdrawal of Microsoft's offer for Yahoo has unleashed a torrent of analysis, second-guessing, high fives, and Bronx cheers.

Just wait until the lawyers get involved.

The expected wave of shareholder lawsuits against Yahoo will have one firm riding the crest: Bernstein Litowitz Berger & Grossman of New York.

The firm has been pursuing a class action against Yahoo since February 21, has been named lead counsel for seven consolidated lawsuits pending at the Delaware Court of Chancery, and has a court order stipulating that it will be the lead law firm for any more suits filed in that court.

"We have been prosecuting it night and day for the last two-and-a-half months," said Gerald Silk of Bernstein Litowitz.

In other words, Bernstein Litowitz and its clients—two retirement funds for municipal workers in Detroit—are in the driver's seat. Lawyers from the firm acknowledge that complaints could be filed in other jurisdictions, but they point out that California cases have already been stayed in deference to the class action in Delaware, where Yahoo (and most other big American companies are incorporated).

Bernstein Litowitz is planning to file an amended complaint later this afternoon, based not only on information learned over the weekend, including Microsoft C.E.O Steven Ballmer's detailed and lengthy letter to Jerry Yang of Yahoo, but also pointing out the myriad problems involved in Yahoo's proposed deal to outsource advertising to Google.

"Yahoo turns around and basically takes the heart of its business and puts it in the hands of Google. How can you rationalize that?" said Mark Lebovitch, the Bernstein partner handling the case.

"We have developed a lot of evidence," he said, and "not just relating to the market's response" this morning to the Ballmer about-face. The firm has deposed Yahoo employees and consultants. "We think we have quite a story to tell, and claims to prosecute," he said. The full story will remain unknown for now: The complaint will be filed under seal because it contains confidential information.

The lawsuit as originally filed claimed, among other things, that Yahoo's board had breached its fiduciary duty to maximize value for shareholders when it instituted a severance package for current Yahoo employees, giving them windfall payments to leave the company if Microsoft succeeded in its bid, at a "cost of billions to shareholders," said Lebovitch. "It would create massive chaos for Microsoft in trying to do an acquisition. They were essentially poisoning the well beforehand."

The complaint sought damages and injunctive relief. "Now our focus turns to money damages and the financial harm that has flowed" from Yahoo's rejection of the Microsoft bid, he said.

Another plaintiffs' lawyer, Stuart Grant of Grant & Eisenhofer, in Wilmington, Delaware, who has been following the Yahoo lawsuits but has not filed one of his own on behalf of the firm's pension-fund clients, expects more cases to be filed and thinks they will have legs.

"The Yahoo board has got some serious problems on its hands," said Grant.

"Delaware law allows you to 'just say no,'" which was Yahoo's mantra during its protracted courtship dance with Microsoft.

The problem, he said, is that Yahoo argued that it was worth more. "On what basis are you going to get there? Have you showed us some long-term strategy that is going to get us there? I think it is difficult to say that this is a business judgment," Grant said.

Some law professors, however, are very skeptical about the potential for success of any breach of fiduciary duty lawsuit against Yahoo

In his letter walking away from the deal, Ballmer essentially equated Yahoo!'s planned linkup with Google to a poison pill. Larry Ribstein, a visiting professor at New York University School of Law who has posted on the deal maneuvers on his blog, said that unlike an actual poison pill plan, which makes a deal all but impossible, the Google linkup "didn't make the deal impossible." And at any rate, management is given leeway by the courts when putting poison pills into effect.

"Basically, the way the courts have interpreted poison pills under Delaware law is that if the board acted in good faith to block the deal, they are still okay," Ribstein said. "While we don't know all the facts, the fact is that Yang was still at the negotiating table: There was still a possible deal."

And while plaintiffs' lawyers play up the mantra that Yahoo!'s board was ignoring its responsibility to "maximize shareholder value," the relevant Delaware precedent is a case called Unocal Corp. v. Mesa Petroleum Co., which allows directors to consider the welfare of the corporation as a whole, including its employees. "Probably the Microsoft deal is better for Yahoo!, but there would have been significant problems in terms of meshing the workforce and employee morale," Ribstein said. The upshot? "I am extremely skeptical, based on what I know right now, that there is a successful shareholder suit here just in terms of the standard breach of fiduciary duty."

And Ribstein doubts that Ballmer is really walking away.

"Ballmer has got to have Yahoo" in Ribstein's view. Facebook or AOL seem very much second best by comparison. "And if that is the case, it is not at all irrational for Yang to play pretty hard ball, if he is the only game in town." So the fat lady has not yet sung in this opera, according to Ribstein. But that probably won't stop the plaintiffs' lawyers from rushing to courthouses to take their chances.