Scott, great insight on "Just own the robots" thesis.  Also, could it be that investors have turned passive in a major way since passive is always cheaper, captures all the upside and beats active over the past decade anyways.  They keep buying more of these companies at any price, regardless of valuation, 'cause what goes up will keep to go up.  And volatility is at all time lows and they're betting that it will stay low.  So far they are right.