Every Sherlock Holmes fan is familiar with "Silver Blaze," the case of the stolen race horse. Holmes solved the case by noting "the curious incident of the dog in the night-time."

"The dog did nothing in the night-time," Inspector Gregory replied. To which Holmes said, "That was the curious incident."

Indeed, sometimes incidents that don't happen are among the most interesting. Here's one that I've noticed -- or rather, I should say, that an intrepid reader has pointed out to me: American International Group (NYSE:AIG) has lost some $60 billion of its market cap, sent multiple executives packing -- including 37-year veteran CEO and Chairman Maurice Greenberg, delayed its 10-K, and admitted to having improperly accounted for transactions with multiple companies, including Berkshire Hathaway (NYSE:BRKa, BRKb) subsidiary General Re. Yet we see exactly zero class action lawsuits filed on behalf of shareholders.

Why isn't Milberg Weiss barking? Where on earth is Bill Lerach?

I take a very dim view of the vast majority of securities class action cases. I see most of them as cookie-cutter filings that are little more than fishing expeditions. Last year, NovaStar Financial (NYSE:NFI) saw its shares pummeled by about 40% in a single day after questions about the company's accounting and business appeared in TheWall Street Journal. Two days afterwards, nearly a dozen class action suits were filed against the company. Whether the suits in that event were meritorious isn't the question I'm after -- though I note that they haven't gone anywhere in the intervening year.

What's interesting is the difference in response. NovaStar's market capitalization dropped by some $300 million that day, and the dinner bell went off. AIG sheds $60 billion, and we can hear the crickets chirping. A look at the list of suits at any one of the big class action firms tells the story: The reaction to NovaStar seems to be the norm; a drop in stock price is sufficient data to warrant a lawsuit on behalf of shareholders. Now we have a case where wrongdoing has not only been alleged by the New York Attorney General's office, but also admitted to by AIG -- a crisis that has dragged on for more than a month involving enough money to make your average plaintiff's lawyer push his own mother under a bus -- and nothing?

Why no lawsuits? Why would minnows like Axonyx (NASDAQ:AXYX) and Audible (NASDAQ:ADBL) rate lawsuits? Why would they bother to sue Tower Automotive, sitting currently in bankruptcy protection, but not sue a gigantic company that has a book value of nearly $80 billion and has offered a clear, direct shot at its Achilles' heel?

I wish I had an answer here. The question to me is fascinating enough.

Bill Mann holds shares in Berkshire Hathaway and NovaStar Financial. He is currently serving as guest analyst for the Motley Fool Hidden Gems newsletter. A free 30-day trial is a click away!

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