Last week, Merrill Lynch's Stanley O'Neal who "retired" after plunging his bank into an $8.4 billion third-quarter writedown that left it with a $2.2 billion loss - the biggest quarterly deficit in its 93-year history. Now, Citigroup's Charles Prince has fallen on his sword with the world's biggest bank facing $8 billion to $11 billion of write-downs related to subprime mortgages, on top of the $5.9 billion reported in early October.

But the problem could be worse. As The Wall Street Journal points out: "Citigroup's subprime exposure - and source of its problems - is found in two big buckets that together total $55 billion in its securities and banking unit, the bank said. The first bucket totals $11.7 billion, including securities tied to subprime loans that were being held, or warehoused, until they could be added to debt pools for investors. The second, totaling $43 billion, covers so-called super-senior securities. These highly rated super-senior securities are portions of collateralized debt obligations, or CDOs. CDOs are repackaged pools of lower-rated securities backed by subprime loans into pieces with different levels of risk and return. Analysts estimate that $60 billion in such super-senior tranches are sitting on the books of banks, insurers and investment funds."

So if the problem is widespread, the question is who is next. When will the next domino fall? Clearly, this is part of a new trend.

"There's a newfound sense of accountability at these boards, but where have they been before? Only now, with a sense of public pressure and a sense of liability that they haven't had before, are they acting," Jeffrey Sonnenfeld of the Yale School of Management has told USA Today.

The next name for the chop that keeps coming up most often is Jimmy Cayne, the chief executive of Bear Stearns who, according to the New York Magazine's Daily Intelligencer, has been forced to send out an email to staff defending himself. Mr Cayne has been away from the office because of ill-health and, with expectations of a fourth-quarter writedown still to come, there has been much speculation that it is time for the 73-year-old to retire.

And let's not forget that the demise of Prince and O'Neal follow the departure of Warren Spector, who left his position as Bear Stearns's co-president after two hedge funds run by the Wall Street firm collapsed, and Peter Wuffli, who left his position as chief executive of UBS, after the bank closed its Dillion Read Capital Management hedge fund.

But the domino theory might not only apply to chief executives.

It could also have an impact on the market. Asian stocks fell after Citigroup announced its writedowns. Clearly, the subprime diaster will continue to take its toll, both on executives and investors.