For Kotaku, posting the roomer was business as usual.
For Sony, blacklisting is just an end to the media favors, as mentioned. It was a desperate reaction to their failure to control the timing and quantity of info/publicity they had been scheming (otherwise it's just a lousy way to react to UNOFFICIAL INFORMATION). They had a nice supply line running, with Kotaku at the receiving end. They noticed a package they thought Kotaku should not have, had an anxiety-filled bowel movement, and eventually burned the supply bridge.
And all this time, the problem wasn't the recipient, it was the underground railroad Sony failed to notice.