Why have trickle-down economics failed to trickle down to the middle-class and poor in recent years?
Trickle-down economics are widely criticized and many believe that it doesn't work. Asher Edelmanon explains brilliantly in the first 2min of this video (or in the written version here).

The basic logic is that, in practice, doing this only leads to a higher accumulation of wealth by the wealthy.