This jump is a result of the Fed getting authorization from congress to pay interest on said reserves. By controlling this rate, the Fed can effectively control how much excess reserves they have, thus having a large impact on the rate of inflation. Having said that, it is a massive and unprecedented amount of excess reserves. If something goes terribly wrong in their exit strategy (and/or the velocity of money picks up unexpectedly) then the worry would be high inflation, not deflation.
EDIT: I believe you meant if inflation kicked in then the flood of free money would discontinue. That would be accurate as interest rates would rise and QE would most certainly be off the table. Deflation fears is what set QE into high-gear in the first place ;)
The lack of inflation despite the Fed's printing can be explained in the massive increase in excess reserves (and also the slowdown in the velocity of money.): https://research.stlouisfed.org/fred2/series/EXCSRESNS
This jump is a result of the Fed getting authorization from congress to pay interest on said reserves. By controlling this rate, the Fed can effectively control how much excess reserves they have, thus having a large impact on the rate of inflation. Having said that, it is a massive and unprecedented amount of excess reserves. If something goes terribly wrong in their exit strategy (and/or the velocity of money picks up unexpectedly) then the worry would be high inflation, not deflation.
EDIT: I believe you meant if inflation kicked in then the flood of free money would discontinue. That would be accurate as interest rates would rise and QE would most certainly be off the table. Deflation fears is what set QE into high-gear in the first place ;)