The dig at "Active Management" feels like it detracts from the article, but I guess they're playing a bit to the audience.

What I found a little more concerning is their glossing over of the liquidity risks. If everyone wants to sell an index, then at some point that index needs to liquidate shares (proportionally). Those shares won't have uniform demand, which is going to cause both price fluctuations (drops) which affect the value of the index. The fun part here too is that this can play some havoc with market-cap weighted indexes, which now need to adjust their holding %'s.