That's one way of slowing the money down. Another is a temporary fix called a "reverse repo," in which the Fed sells assets back to an institution, with a promise to buy them back at a later date.
The idea of simply winking money into and out of existence seems strange enough to those of us who don't have that power. What may be even stranger, however, is that even if and when this money disappears from the money supply, it can leave real value behind. For instance, the Fed, like any other investor, gets a return on the assets it buys. In 2011, it earned roughly $77 billion in profits, mostly from interest. The Fed's profits are remitted back to the Treasury, which the Fed has argued saves taxpayers money. As Bernanke said at a congressional hearing in 2011, "It's interest that the Treasury didn't have to pay to the Chinese."
There are plenty of other potential effects, of course. Opponents of easing fear an inflationary spike, as an influx of dollars devalues the currency. Meanwhile, the Fed hopes that the purchases can help jumpstart the economy, particularly a depressed housing market. That's a lot of economic change, especially when you consider that, in certain ways, it came from nowhere.
Danielle Kurtzleben is a business and economics reporter for U.S. News & World Report. Connect with her on Twitter @titonka or via E-mail at firstname.lastname@example.org.