When sustainable real growth is in sight, banks will want higher returns and start lending at a quicker pace.

FORBES: Bernanke Administers Another Cruel Dose Of Financial Morphine With QE3

Not only are banks unable to continue lending at anything like their previous pace, but capital markets are now sucking money out of the diminished pool available for mortgage lending.

ECONOMIST: Housing market

But the pace of bank lending is unsustainable, and America's recent experience suggests that it is better to prevent bubbles forming than to mop up the mess afterwards.

ECONOMIST: Is the economic stimulus too much of a good thing?