How many traders look only for network latency, extremely few I would say. Why is this, simply because it is so rare and it takes a lot of effort monitoring. The easiest way to solve the latency issue is to give a re-quote or a 'price no longer valid message' (what they are in fact already practice excessively). Is there any network latency trading DMA, of course, you will not get filled, or there will be some slippage, depending on what kind of order you have. The latency issue counts for such a small percentage (probably per thousand) that it does not justify Simon's standpoint on this issue, or the number of traders being flagged and categorized. furthermore, it is absurd to transfer the responsibility and the validity of a price quote to the client.