Sony tried to get some hackers arrested (George Hotz aka geohot, graf_chokolo) earlier this year for hacking their PS3s. This had nothing to do with the network infrastructure. There was a feature that Sony removed from the PS3 in a somewhat recent firmware update (3.21+) - called "OtherOS" - which they believed was causing rampant piracy and therefore it needed to go.
PlayStation Network presentation -TMG
Well a lot of people weren't too happy about this, and there is still an ongoing court dispute about this wherein many claim that the removal of the feature is like some sort of misleading advertising. Anyway, one hacker in particular has been targeted by the company in this dispute, and a hacker group called Anonymous has also made some statements about the removal of this feature - claiming it is unwarranted.
It could be that this intrusion into their network infrastructure was in part due to the backlash from this earlier feature removal.
The Anonymous group has come out and said that they had nothing to do with this latest attempt, so if Sony can find these guys only time will tell. But if they can't, then this will be one of the most successful disturbances of business we've ever seen.
The Anonymous group is also well known for their attempts at Distributed Denial of Service attacks or DDoS. They aren't known for stealing credit card information nor have they demonstrated an ability to make such attempts.
I'm pretty sure from here on in, Sony will make damn sure they have a good anti-piracy schema in place from the beginning of their system's hardware cycle. People have proven time and again that they will go to great lengths to cause civil unrest or corporate disruption if they feel they've been treated unjustly.