Earlier that year (in September), a market glitch led some ETFs to trade at prices double that of their underlying values. In addition, many traders were not happy with the quality of trade execution...

Earlier that year (in September), a market glitch led some ETFs to trade at prices double that of their underlying values. In addition, many traders were not happy with the quality of trade execution on ETFs. That is because sometimes brokers used a market order rather than a limit order (recall that a limit order instructs the broker to buy shares only if he can find them at or below a given price, not at current market prices).