This isn't what HFTs do. One common HFT trick is exactly the opposite of what you wrote: they'll attempt to identify probable sellers of large blocks who are d

This isn't what HFTs do. One common HFT trick is exactly the opposite of what you wrote: they'll attempt to identify probable sellers of large blocks who are disguising their actions by using smaller blocks (they can identify this by measuring latency orders arrive at different exchanges), and then using knowledge of the order books at different exchanges to buy the large block at 10.00 from the seller who was already committed to sell and then sell it at 10.02 to the buyer who was already committed to buying. They can do this because the institutional seller is using the NBBO based on the SIP, and they're watching 200micros ahead using direct feeds.