Activist Renews MBIA Fight

Bad news for monolines, however, may mean boffo returns for others.

Ackman said his short bets against Ambac and MBIA could result in hundreds of millions in profits. He has earned respect on Wall Street by agitating for change at McDonald's(MCD Quote) and most recently Target(TGT Quote).

Ackman has been betting that the stock of MBIA will fail since he published his research report five years ago. He said during the Value Investing confab that if he is right, he will donate his personal share of the money he generates to charity.

Pershing Square has about $6 billion of assets under management.