The unending efforts of our glorious central-banking planners to raise asset prices and encourage 'animal spirits' through the trickle-down of unicorn-tears via the wealth effect have side-effects. Unintended consequences of 'leaking liquidity' finding its way into hard assets and 'things that have relatively limited supply' have stalled hopes of a stimulus in China (food inflation) and caused refis to mysteriously lag on misplaced future rate expectations in the US (ZIRP). The biggest 'problem' the central-bankers face, however, is energy prices. The liquidity surges directly impact the price of oil (which is already under pressure from the ever-igniting fears of Middle-East flare-ups). Critically, as Goldman notes, once the price of Brent crude reaches $125, global economic growth becomes challenged and ultimately makes QE self-defeating. This means Bernanke and his cohorts are threading an ever-narrowing needle as crude's price range remains high enough to motivate supply, but not so high as to undermine the global economic recovery - and with a tight physical market, any disruption or 'anomaly' will be hard to jawbone us back from (SPR rumors aside).
Brent crude oil prices over $125/bbl have been followed by a swift deterioration in economic growth.
[9]
Brent front month price in $/bbl (lhs);
Goldman Sachs US Economics MAP Index (rhs)
Chart: Goldman Sachs