Interesting - reading about that now in an FXCM article (http://www.fxcm.com/advantages/forex-execution/compare-execution-types/). Thanks, fp. It alludes to reactions made by DD counterparties in the 'Order Execution' section: "Scalping is allowed, but FXCM reserves the right to manage its risk by changing your execution type. While forex isn't the asset class of interest for the question, it is of course ancillary (esp to CME currency futs), and seems a valid contextual example of brokers hedging/building a position in their book off of the customer's, per their discretion.