Quote from sirgiyan:
I can explain it only to the certain extend (otherwise I wouldn't ask for more interpretations)
When liquidity drops like this (never happened for the last 3 years BTW) you've got huge swings of price in either direction and it take more time for any order to be filled.
It means that trading becomes much more dangerous. In fact we saw a small preview of this last week with big gaps up and down almost every day.
Although I tend to interpret this as a last nail in the coffin of this rally - I can be wrong. Anyways it's better to be alert and not to trade too much this week (overtrading is a bad thing anyway, but this only reinforces this truth)