As we have seen Island and Inca have been forced to stop publishing their quotes in the SPY's ,, etc.. I guess they had become too popular and where doing too good a job of providing a open, electronic marketplace. Anyway, most of the volume has gone to ARCA - because they can still publish quotes until they exceed 5% of the volume for 4 of the last 6 months. However, ARCA and the Pacific exchange are partners -- and when you look at a level 2 of the spy's with the regional exchanges - you will notice that ARCA quotes are really the same as the Pacific -- so I think that even when ARCA is forced to stop publishing their quotes -- you will still be able to see where the ARCA market is by looking at the regional Pacific quotes - which will show the best bid and ask -- ??????