The Fed recently reaffirmed its determination to expand its balance sheet. The crisis has already driven it to take on risky assets such as agency bonds and commercial paper. It has also lent to weak financial institutions, and is expected to participate in the Treasury's public-private partnership to buy toxic assets. The expansion has averted a crippling credit contraction. But the Fed could lose money by taking on risk.
Update (5/26/2009): Per suggestion from C.F. Reader