At a broad level, there's evidence to suggest that large scale asset purchases are only marginally effective at driving demand and relieving disinflationary pressures (the fact that the latter is an explicit goal of monetary authorities rests on the a priori assumption that lower prices are everywhere and always a bad thing) and to the extent that they achieve those goals at all, the effect dissipates with each successive round of monetary madness. In the mean time, the effect on the middle class, savers, and financial market stability is catastrophic and unlike the purported benefits of QE, the negative effects grow (in some cases exponentially) with each iteration. 

The end result is an entire class of savers devastated by negative real returns (even as the government is able to sustain what would otherwise be an unsustainable debt burden), a widening of the gap between the wealthy and everyone else (by virtue of the fact that the wealthy hold a larger percentage of the types of financial assets which benefit from QE), and perhaps most importantly, the inflation of asset bubbles and the fostering of market instability via manipulation and distortion. 

Why is the latter the most important point (that is, negative real rates for savers and the destruction of the middle class would seem to take precedence over distortions in financial markets which are the playground of the rich)?