Earlier quoted context omitted.
Umm, yes and no. Example, I'm Fidelity Bob Fund Manager; after extensive research, I decide to make a decision to buy 200,000 shares of AAPL. So I enter my buy order into my OMS screen, which slices and dices these 200,000 shares into blocks of 100 shares (as for traders not to front-run me, because a naked buy order of 200,000 shares will drive the price up and I'll overpay long after my transaction is completed). H…
But HFT dealers stopped trading that day is not entirely true. Some HFT traders (not dealers) stopped at the flash crash, but others stayed in, partly because they were obligated to due to their liquidity agreements with the exchanges, and partly in retrospect to make bags and bags of money. If the latter were not in the market, you would not have seen the flash-uncrash that was the recovery, and it would have been 1…
If the dealers don't want to trade, they just make their buy and sell limit orders to be way out of the normal price band. Hence, I want to buy Accenture at $0.01 and sell Accenture at $1000. Yea, I'm meeting my exchange contractual obligation, but who's going to trade with me now?
What happened during the flash-crash is that people's market stop-orders were getting triggered after the initial crash, when the market went down 20%; when all other human traders stepped out of the market, but there were still tons of market stop-orders to sell; guess whose limit buy orders were matched? Accenture buy order at $0.01.
To be fair though, a lot of those ridiculous trades were later busted by the exchanges. But the irony of the whole crash is that the HFT traders actually fanned the fire on the crash and then later rode the wave all the way back up (for the trades that weren't busted anyways).