Somewhat Correct, Somewhat Wrong sir
It 'is' partly true what you say Cuppa T. Companies (game companies included) usually hire a third party to build up their security and their defenses. I don't know whether that is the case with the PSN (my knowledge of Sony history and systems reliance is very limited), but I can tell you that if that is the case, then Sony is only partially to blame.
Partially because they should
a) have checked on the defense measures themselves to be sure that is was really as good as they wanted it to be.
b) Also the first and the best thing to test a system defenses and reliance is to try to crack it themselves with hired Hackers before putting it out to the public, not doing that, at least search for loopholes in, this is a standard procedure for most companies that wants their system security to be taken seriously.
c) Even if they did all this and didn't find any loopholes they should always be careful and on full watch, especially when updating said system.
(Rule nr. 1 (or 20 or 234) for securing patches:
Companies should Always, and I mean always, test out whether something is wrong with patches by using an isolated system before making the patches open for the public. Sony is a wealthy company so there should be nothing hindering them from doing so.)
But partially not because
a) The third party company who is hired to build up defenses for system(s) are expected to make it properly and with as few as possible weaknesses.
b) They are usually contact bound to take responsibility of maintaining said system(s) and come up with fixes when loopholes/weaknesses in the walls are found. It is a serious rift of the contract if they do not.
But if they built up the defenses themselves, then oh dear! I would not want to be in their shoes right now. Nothing is scarier than many millions of angry customers.
EXTRA! READ IF INTERESTED!
Note of advice here people! If they did screw up on this but you didn't receive any damage to your account neither in the PSN nor in the Bank. Please refer from suing them... Sony is a wealthy company, but it can NOT handle being gangb*** by such a huge angry mob. It would make the game part of the company broke without a doubt.
And even if they totally f***ed up this time (excuse my language) the people that work for the various branches of the company should not have to suffer from the incompetence of a small group of people.
Do you really want that the people who made those games
lose their jobs?
NOTE: If there is something out of place here or wrong in my reply, please just let me know. As I said before, nothing is mettled in stone, not even my opinion. If new information comes into daylight then I see nothing wrong with adjusting my view according to those evidences.