ETFs are a collective grouping of securities where valuable knowledge at the extremes of opportunity or disaster is washed out into an average.

The previous financial crisis was precipitated by a trend where perceived value broke from reality. Then it was mortgage backed securities (MBS) breaking the link from a banker's knowledge of his customer and local real estate conditions and substituting it for a financial rating agency's grade. One could posit that today's market decline and impending crisis will be identified as coming from electronically traded funds (ETF) which break the link from an investors knowledge of an individual security and substitutes it with a description of a collective grouping, an index, of securities where valuable knowledge at the extremes of opportunity or disaster is washed out into an average.
Luring Investors into even Narrower Niches reports on a trend to a particularly wrongheaded assumption that results are enhanced  by focused rather than scatter shot investments in a new and upcoming field such as robotics.  What is the investor's hurry? Buying early into a group of companies dissipates the advantage of having bought early and inexpensively by mixing a possible winner among outright going out of business failures especially when time and analysis can cull out the losers and direct you to a real chance of finding the winner.