Quote from Kensho:
Rearden, in regards to stop loss orders...if you had a stop in place on that infamous day when you lost 2 million in minutes maybe you would've ended the day up one million instead of down one. I agree with the other two points.
On a move like that, stop orders would not be effective. They won't be magically filled at a price that the stock gapped right through.
I agree with Rearden. Stop orders are amateur, with the exception of swing trading. I don't know any active traders that use hard stop orders. Even the thought is laughable.

