A new thread on a topic that's been bothering me lately: Any thoughts on ATSes providing non-disclosed liquidity (Millenium, Liquidnet, etc) -- how their increasing use by institutions may impact liquidity availability for smaller orders? Will regulation NMS increase their use, as buy side players who want to fill a big order outside the NBBO can do so via a dark pool w/o having to potentially fragment it while meeting NMS requirements on a national exchange? Is there anything brokers can/are doing to stay ahead of the growth of dark pools to better support the non-institutional trader's access to liquidity? ECNs changed the market slowly but surely over the past several decades (primarily in the last 15 years). Will dark pools be next and if so, how do can retail investors benefit and not be shut out?