Theres a story here on www.traderbulletin.com that says NexTrade can display its ECN orders on both superMontage and the ADF. Does displaying on both venues actually help, or improve fills. If so how? Mind you NexTrade isn't the world's most liquid ECN to begin with.
When you display on the ADF it does not provide a median to execute on. So to trade with that quote you have to route to the venue displaying. e.g. a direct link to that ECN On SM the qote can be executed against. So there is small exposure of duplicate trading on behalf of the ECN but when things execute/reject/cancel in nanoseconds it is not a great risk. It does nothing to increase the liquidity of the ECN because it is the same volume being shown in the qote at both display facilities. Ciao....