Hi Rolly, All,
This addresses your comment:
"Rapid traders seemed absent last thursday. Price didn't flucuate that much.."

I don't pretend to fully understand this HFT business, but I have read thoughts that the 1 min. bar on the intraday chart right at 10.30 am Thurs. was the result of HFT. i put a chart segment below. The OHLC of the bar was 3.457, 3.457, 3.401, 3.438.

I agree that what came before and a couple of minutes after was fairly benign as Thurs. reports go.
Unfortunately I failed to show the volume of 3511 contracts, which was high. Look at a chart.

Unfortunately on that long "down shadow" you don't know how many contracts actually traded down at those levels.

I clearly don't know how this actually works out, but it looks like "if someone with deep pockets" wanted to buy in quantity, they would issue "successively lower bids" until the offers started to roll in and they would buy them up until they had exhausted their capacity/interest to buy them.

In any event in this case, it looks like they would have achieved their goal, and then price went on up.
- All I can say here is that the view of the market must have been that this event would not trigger a major selloff and it would re-bound.

I have read stuff that the algos are "so fast" that the "bid/ask" is actually manipulated "triggering trades" ???? I question that, but maybe ??? In this case from what I can see, actual trades took place, stops were triggered and the contracts were bought up - even tho very quickly !!!!

Don't these sudden, large swings prevent the smaller retail traders from using sensible stops ???

I'm not sure when this HFT business really started in earnest, but I might wonder if it is not the "new answer" to the "mortgage market" to pay for those big buildings on Wall Street !!!!!

Going back a few years, I have been in most of those Bank and Brokerage houses "trading rooms" - better yet "read FLOORS" supported with all of their "mainframe computers" etc. etc. You didn't compete with them, you just tried to "identify what they were up to" and go along for the ride !!!

Now, what they seem to do is simply use their "wealth and computing power" to "dump a market, grab what they can" and move on to the next !!!! You can't compete with that !!!

I say this here to intentionally try to trigger some comments:
HFT at best is bringing in an era of "no stop trading" where you must have the confidence in the market you are trading such that these "lightning bolt" transitions will recover before your broker closes you out !!!! Otherwise you might as well stop trading because your "piggy bank" will never be big enough to compete with "Wall Street" !!!

Think about it,
Lee