After all of the talk of splitting itself into two pieces, a "bad" part and a "good" part, Ambac (NYSE: ABK) will probably operate as only one company. The theory had been that the healthy muni-bond insurance operation should be separated from the business that insured more risky derivative instruments.

Breaking the company in half always had a number of complications, the worst of which is what would happen to common shareholders? Would they get shares in the "good" part of the business? Perhaps, but outside firms putting in money might want to keep that for themselves. Shares in the "bad" part of the business would probably be worthless.

Another issue is the legal troubles a split might cause. According to the FT, this raised the "possibility of lawsuits by banks and other groups that bought insurance on CDOs and other structured products."

Ambak is almost certainly going to have to live with its two businesses under that same roof. If the structured finance business continues to fall apart, the real question is how much more money will the insurance company have to raise.

Douglas A. McIntyre is an editor at 27wallst.com.

The good news is that MBIA (NYSE: MBI) saved its S&P "AAA" rating, meaning bonds it insures will not lose their value. A drop in the rating could have caused write-offs at banks that own paper covered by the bond insurer.

MBIA also announced yesterday that it will, sometime in the next five years, break its muni-bond insurance business from its structured finance operations, forming two companies. Structured finance bonds have lost much of their value because they include CDOs and mortgage securities.

The move may have helped save the company, but it comes with a huge cost. MBIA is eliminating its dividend to save $174 million a year. For investors taking advantage of the company's 10% yield, the news could hardly be worse.

MBIA may have bought itself some time, but it put the wood to shareholders to stay afloat.

Douglas A. McIntyre is an editor at 247wallst.com.

It seems as though every week, the public is forced to learn another one of Wall Street's strange names for a surefire deal that couldn't miss. But the reason we're learning about those strange names is because -- contrary to promises -- the can't miss deals are shutting down -- taking Wall Street's credibility down along with them.

The latest of these is auction rate securities (ARSs) -- a $330 billion market for long-term bonds that are supposed to pay lower rates because their interest rates are set through auctions. The New York Times reports that municipalities who issued ARSs are suffering because 1,000 of these auctions failed and instead of paying 3% interest rates, they have to pay 20%. And if that wasn't bad enough, the investment banks that oversee these auctions are refusing to let investors withdraw their money.

Which investment banks are imposing this pain? Goldman Sachs Group (NYSE: GS), Merrill Lynch (NYSE: MER), and Lehman Brothers Holdings (NYSE: LEH) and the problem with ARSs is not limited to municipalities entities such as the Port Authority of New York and New Jersey. Closed-end mutual funds, student loan companies and corporations also issue them.

The New York Times fingers hedge fund manager William Ackman for yesterday's down market. That's because Ackman has been a vocal pioneer of the idea that bond insurers lack the capital to back their bets on the solvency of the bonds they insure and they might lose $24 billion as a result. And the holders of those bonds are banks and insurance companies which will be forced to write-down the value of those bonds -- to the tune of $70 billion more -- if the bond insurers lose their AAA ratings.

I wrote about Ackman's bet against bond insurance last May. If you had followed my suggestion to follow Ackman's short sales of MBIA (NYSE: MBI) and Ambac Financial Group (NYSE: ABK) you would have profited from the respective 81% and 89% declines in these stocks since then. And as a protege of Harvard Business School Professor Michael E. Porter -- with whom I worked -- I admire Ackman's analytical skills and his willingness to put money into his bets. Moreover, Ackman pledged to give the profits from his bond insurance short sales to charity.

But Ackman's estimate of the losses from downgraded bond insurers is big and scary. His report yesterday predicted that MBIA and Ambac might lose $24 billion on the CDOs they guaranteed. That $24 billion is a significant percentage of the $1 trillion in municipal, corporate and mortgage debt that they insure with their AAA ratings. Unfortunately, ratings agencies like S.& P. and Moody's Investors Service may downgrade them due to a lack of capital relative to their potential losses.