"The Fed is also vulnerable to losses through its so-called Maiden Lane portfolios, a collection of investments it acquired when it brokered J.P. Morgan Chase's takeover of a floundering Bear Stearns and bailed out failed insurer AIG.
The portfolio will likely generate losses, according to many analysts. Still, the total Maiden Lane portfolio amounts to just $66 billion, a small slice of the Fed's growing pie of securities.
For most Fed officials, a concern over credit losses would be a luxury compared with the risk they see as predominant: that the economy will not grow quickly enough to return more than 14 million unemployed Americans to work, and inflation so low that it leaves the country exposed to possible deflationary shocks.
"The risks are worthwhile given that the economy would be in the toilet if the Fed never did anything to expand its balance sheet," said Michael Feroli, chief economist at JP Morgan and a former New York Fed staffer.
Feroli does not believe asset sales will be a primary avenue for the Fed's exit. Indeed, Bernanke appears to think the ability to raise interest rates on bank reserves might prove the most effective way to withdraw stimulus. But even that tool is not without its mechanical difficulties.
The problem lies in the basic workings of fixed income. By definition, bond prices decline when their yields or interest rates go up. That means that as the economy recovers and pushes inflation higher, the Fed will move to increase interest rates, pushing down the value of its giant bond portfolio.
"What would the international reaction be if the Fed suddenly had to go and be recapitalized?" said Bob Eisenbeis, chief monetary economist at Cumberland Advisors and a former head of research at the Atlanta Fed. "I don't think that would bode well for Treasuries, or for the dollar, or anything else. It would be embarrassing."