This is a good summary of a typically rational article by Matt Levine. His entire commentary on the industry post-"Flash Boys" is similarly enlightening and balanced.
There is a striking parallel in the futures markets: Their original role was to help farmers hedge their risk of bad harvests by setting a fixed price for future delivery of foodstuffs. That market overtly and explicitly requires that there be hedgers and speculators, otherwise - no trade. Dark pools are no different, for the reasons you nicely outline above.
You could argue that what Barclays really should have done was channel some retail flow into LX, but sources of that kind of unlimited, innocent liquidity get snapped up pretty quickly.
There is a striking parallel in the futures markets: Their original role was to help farmers hedge their risk of bad harvests by setting a fixed price for future delivery of foodstuffs. That market overtly and explicitly requires that there be hedgers and speculators, otherwise - no trade. Dark pools are no different, for the reasons you nicely outline above.
You could argue that what Barclays really should have done was channel some retail flow into LX, but sources of that kind of unlimited, innocent liquidity get snapped up pretty quickly.