Of course HFT is not the root cause, it might have burned the fuel(stops) when acceleration approached terminal speed. However last tuesday and even before that

Of course HFT is not the root cause, it might have burned the fuel(stops) when acceleration approached terminal speed. However last tuesday and even before that VIX was on record heights and it pushed even higher today. No fat fingers then. Market is trying to tell us something, obviously. Cumulation was there, this was just a first in a series of explosions triggered by one reason or the other (greece/eu/trichet inaction today).