[simplemath]

Except that what's happening is that the order is against a "cart" with sufficient inventory to completely fulfill the initial order, and other actors are interrupting the transaction to add carts 2-n. Is that not the case?

[noonespecial]

I'd say its worse than that. As you reach for each apple in the cart you've chosen, someone with an empty cart runs over and grabs it just before your hand can close around it, takes it back to his own cart and marks it up a few cents.

[laichzeit0]

Not for each apple. At the very worst case you get the first apple you tried to reach for. After that all further apple prices may change. Then you can reach and take another one and all further apple prices may change, etc.

You'll notice that there was a quote at exchange A and exchange B. You reached for, and got, an apple at exchange A. Now you're trying to reach for an apple at exchange B and you're surprised that it's a different price.

People are mostly pissed because the time between reaching for the apple at A and B is so fractionally small that they feel there shouldn't be a difference in price. That's really the only issue they have.

[mmaldacker]

It's not the case. The trader wanted 20 000 shares, there was a combined amount of 24 800 shares, i.e. every exchange had less then 20 000.