Article suggests Sony has known about security issues for a while

 http://arstechnica.com/gaming/news/2011/02/report-psn-hacked-showing-stunning-lack-of-credit-card-security.ars

This is article is two months old, and it's pretty damning.

Here's an interesting quote: "We've contacted Sony for comment, but have not received a reply at time of publication. The hackers joked that the next update will remove the PlayStation Network, just as Sony removed the Other OS feature when it became compromised."

Here's the supposed conversation between the hackers in full:  http://pastie.org/private/97oth9v5tspkiztwwdmnga
Notice the date on that conversation. February.