How much fault should be placed on Sony for the infamous hacking that occurred just recently?

I was discussing the recent (and still ongoing) hack of Sony’s network with a friend. We disagreed on where the blame should be primarily placed.

I have a hard time finding who I should be more upset with; hackers or SONY.

Should SONY take the blame for not properly securing their networks to the point where hacker group after hacker group was just having a run at their systems? I mean Sony did pursue the infamous hacker George Hotz which leads me to wonder Why didn’t Sony better prepare themselves for the hacker backlash?

Should hackers be to blame for obvious reasons? I understand a large sum of people despise hackers, especially those who steal the credit card numbers and identity of people.

Who upsets you more? Sure, you might be upset with both, but who should take the most blame?