Yes---more doubt now than ever as pathetic jobs numbers prove that QE is NOT helping to create jobs...and since it's ineffective, probably time to start winding down. Why throw more good (play) money after bad?
There can always be doubt of continuing bond purchases with created reserves that raise inflationary expectations. As a result of such programs, numerous 'black swan' end game scenarios could arise, such as a sudden and dramatic rise in interest rates and/or currency dislocation. It is most likely that this will occur in Europe and Japan first, but could well happen to the U.S. thereafter. You can guarantee that if intermediate to long-term Treasury Securities begin to dramatically fall in price, the Federal Reserve will have no other option but to follow the markets, not only ceasing further bond purchases, but exponentially raising the Discount and Federal Funds Rates to stymie higher interest rates and/or a currency run on the dollar.
--- As a result of such programs, numerous 'black swan' end game scenarios could arise, such as a sudden and dramatic rise in interest rates and/or currency dislocation.----
Why do you think a dramatic rise in interest rates could occur with this strategy? It's been roughly five years now since the Fed started this and there is no sign this is going to happen. Do you own a black swan farm?