After fending off most challenges to its independence and winning new powers to oversee big financial firms, the Federal Reserve has emerged from a bruising debate on the overhaul of U.S. financial rules as perhaps the pre-eminent regulator in the sector. But that could only bring it added blame if things go wrong again.

Just a few months ago, amid populist anger at the Fed for failing to prevent the financial crisis of 2008 and bailing out Wall Street, Congress was talking of stripping the central bank of its supervisory oversight of banks or forcing it to submit to congressional audit of its interest-rate decisions.

Instead, the new law gives the Fed more power and a better tool box to help prevent financial crises. It will become the primary regulator for large, complex financial firms of all kinds, such as American International Group, the insurer which built a massive derivatives portfolio that regulators didn't see until it was too late.

This isn't the first time Congress has expanded the Fed's role. After the Great Depression, it passed the Employment Act in 1946, charging the Fed with averting the huge unemployment seen in the 1930s. After the double-digit inflation of the 1970s, the Fed was formally given a dual mandate of promoting both price stability and maximum sustainable employment. In the wake of the latest financial crisis, the Fed is effectively being told to add the maintenance of financial stability to its responsibilities.

The risks, however, are that the Fed still won't be able to prevent another crisis, and that it will be an even clearer target for blame if that occurs. "The bill has good intentions, but I'm worried about its implementation. If I were the Fed, I'd be seriously worried about being left holding the bag," said Anil Kashyap, a professor at the University of Chicago's Booth School of Business.