Quote from OldTrader:
Perhaps you would like to expand on this: what lack of foresight was there was there when the electronic markets were set up?
The currently operating electronic markets lacks the locals, market makers, and/or specialists to absorb order flow imbalances. So... when there are significant order flow imbalances, and/or stops outnumbering limit orders, the excessively simplistic rules of the match engines causes the electronic market to cascade out of control. That wouldn't be so bad, but the random busts mean greater risk than reward for people who want to step in and correct the error.
The problem was foreseeable because the exchanges knew from over a century of experience the value that the locals, market makers, and/or specialists add. What's worse, after they've been repeatedly shown what they screwed up, they're just trying to make it less likely with stupid band-aids like limited trading ranges, maximum order sizes, maximum slip on a stop, etc. BUT, when North Korea nukes Japan (or whatever), those band-aids are going to hurt a lot more than they help. People will be happy to get filled 1% down, and some will desparately need to get an order in to sell 3,000 contracts ASAP.
The actual solution is so simple, I don't know why they didn't do it in the first place. It doesn't require unfair policies, or violating any of the current rules. At least BOX may be heading in the right direction.