"The Fed will finance these programmes with newly created reserves: that is, it will print money. Its balance sheet, which has ballooned from $900 billion to $2.2 trillion since August, could grow by another $800 billion, making it a larger lender than any commercial bank.

[...]

"Yet these strategies do carry risks. One is inflation. Having expanded its balance sheet so rapidly, the Fed may not have the foresight or courage to shrink it fast enough once the crisis passes, and the extra liquidity could fuel an overheating economy. But with unenployment perhaps heading for 9%, from 6.5% now, that risk seems remote. Another risk is that the Fed and the Treasury have taken on more commitments than they can credibly keep. With budget deficits that could top $1 trillion a year, plus trillions of dollars more in guarantees to mortgages and bank debt, some investors may question America's ability to shoulder the dollar, although with the entire world in recession, that lack of appealing alternatives makes that less plausible." (The Economist)