[wj]

Retirees might need to liquid a percentage of their portfolio each month to pay their bills. Getting caught in a flash crash can have an effect on them.

In a general sense though I agree that the behavior shouldn't be illegal but am fine with exchanges implementing rules about it. For a trade to occur both the buyer and the seller are getting what they want at a price they both deem acceptable. Phantom orders does not inherently change that.

[tedunangst]

Keep in mind that you're talking about getting caught in a window that was 34 minutes long. So you'd have to be pretty unlucky, not to mention oblivious, to push through a market sell order at that time.