First of all, this has nothing to do with Geohotz or any other PlayStation3 custom firmware development (it does not appear that custom firmware would have been required to undertake or discover this attack).
Secondly, it does not appear to have anything to do with AnonOps (the particular Anonymous group undertaking a protest against Sony's litigation) either; this does not in any way resemble their chosen method of protest, and they have formally denied responsibility or involvement. I am familiar enough with their methods, basic as they are, to state that there is no way that they could have been responsible for this, or would have had any idea: LOIC is essentially just while true { visit website }, and that's not going to bring this kind of thing to light.
To simply state that this is the result of an external intrusion is, in my view, misleading. Sony have chosen to take the PSN system down; Sony designed it in-house in the first place. I'm not familiar with any external third-party security auditing they did of their systems, if indeed there was any until 19th April 2011 (I doubt it). Sony have chosen not to make a public statement of any particular substance until now, a decision for which they have been widely criticsed. The security vulnerabilities that have come to light in the PSN system are entirely due to Sony's incompetence and negligence; whether any malicious crackers have in fact exploited them or not, they are now at least partially known.
I don't have any detailed knowledge about the specifics, but from the rumours floating around, it appears that someone discovered it was possible to download games and DLC on the PlayStation Network without paying for it, by simply changing a URL parameter of some kind (I don't know any details; in any case, it's moot now). The implication was that this was surprisingly easy; upon further investigation, the security on the PSN as a whole was found to be exceptionally poor, and the discoverer expressed surprise and disappointment about this. I do not know if, or when, the vulnerability was reported to Sony.
It appears that Sony have been logging via PSN everything you ever played on your PS3, and storing, and in some cases even transmitting, personal details - including names, addresses, passwords and even credit card numbers - in cleartext; sometimes with no encryption. Furthermore, apparently their backend servers run (or, rather, ran) a known-vulnerable version of Apache for an extended period of time. That's a level of security far below anything anyone (including international PCI DSS card-processing security standards) would expect from a retailer of any kind, let alone a major international retailer. It's irresponsible. It's negligent.
One of the basic rules in security research is this: try not to shoot the messenger. Do not blame a hacker merely for discovering that someone was incompetent; instead, fix the hole, figure out what the impact was, try to deal with the impact, and figure out why the hole occurred in the first place and deal with that.
Even now that it has come to light, we can never know if the most recent ones to discover it were the first to be aware of the issues, or if someone more malicious has been exploiting them for some time previously. The issues do appear to be so widespread and simple in nature that it is not impossible that they have been independently discovered before by parties unknown. Equally, there's every possibility that in fact, subscriber's personal information hasn't actually been stolen by any malicious crackers in particular; but Sony have had to react this way because it could have been, at any time, probably without Sony's knowledge.
I'm very disappointed in their incompetence in actually bringing live such a misdesigned system. I cannot believe that they have actually passed any industry audits, and their utter failure to communicate any details about such a massive breach with the public for so long in my opinion warrants a detailed public investigation. I doubt Sony would be comfortable with that, but only because I doubt their ability to be able to pass an audit with such scrutiny.
tl;dr: Epic fail, Sony.