I'd be interesting in finding out how they are going to implement the 'stops logic.' This logic would have to involve not honoring stops placed outside the market under certain conditions. This has happened enough times for me to think that some wiseguy is arbitraging the difference bet how the floor and how electronic markets handle large block orders. If you dump a bunch of contracts in the emini, it can move alot faster and further than the floor would. That difference might be enough to exploit profitably. On the floor, there's a self correcting behavior that prevents these spikes from building momentum: spikes tend to get faded. However, if the seller is way too big (like in the crash of '87), then the locals would back away and there would be a no bid condition which would be resolved only when the seller cancelled or the book got filled back up with bids at a much lower price level. In either case on the floor, you don't get a condition where stops trigger more stops. The floor trader isn't going to stand there and get taken out by the big seller. They'll move away from the seller. In the electronic market, things can move so fast that the entire book can be cleared before people really have a chance to modify their orders.