Will these policies mitigate the risks of future financial crises? Will they support long-term economic growth? Now is not only a time of consequence for regulation and the U.S. economy. It is also a time for choosing.
A second set of costs has to do with the possible effects of further asset purchases on various aspects of market functioning, including bid-ask spreads and market depth. And it would indeed be a concern if large Fed ownership of some segments of the Treasury or MBS market were to cause market liquidity to deteriorate significantly.