That's what it is: People are seeing the orders pour through the various exchanges, and are reacting to it. If they were seeing the orders before they hit the exchanges, that would be front running, and it would be illegal. But Nanex appears to be showing people responding to orders after they hit the exchanges, and that would seem to be legal and moral.
The moral is that if you want to buy so much of a single stock that you can't even buy it all from a single exchange, you MAY end up paying a bit of a premium, unless you're quite good at hiding what you're doing. And in this example, the purchaser was not. It's a story as old as markets.