The reason for the attack is in retaliation to a law-suit
Summary: The Sony PS3 console was "hacked" or more appropriately, jailbroken, by iPhone hacker, Geohot.
He managed to reverse engineer his own Playstation 3 to run homebrew applications on it.
And then later released the method to the public, through his site, geohot.com
Sony hit him with a lawsuit and demanded social media sites, including YouTube to hand over IP addresses of people who visited Geohot's social pages/videos.
Paypal have granted access to Sony for them to view Geohot's paypal account.
The judge of the case has given permission to Sony to view the IP addresses of everyone who visited geohot.com
Sony are also after another group of hackers for the same case.
The PS3 hack which GeoHot released can be compared to the "unlocking" of a phone.
i.e. Once you purchase the phone, it's yours, you can do whatever it is you want with it.