Peter, I don't think that's fair or accurate. Anyone observing the chain gets proof of publication of matched orders, and a filtered average over the last N blocks gives you a relatively good idea of the current price in a secure way which you can compare with what you're seeing on the wire. Additionally, such a setup does not rule out the possibility of other proof-of-publication systems being used for distributing the orders. It simply recognizes that consensus over matched trades and consensus over open orders are logically distinct, and data from one need not clog up the other.