" People don't just hack online networks! This isn't just a matter of Sony got unlucky, this is a matter of Sony let a lot of people get screwed do to lack of proper security infrastructure. If this isn't Sony's fault than why is it we never see crap like this happen to Xbox live or Steam? Oh yeah! because they have secure servers! (I'd assume) "You are correct.
A hack means that someone attempts to modify/change/adapt/gain entry into something. To do so they exploit a bug/flaw/hole in the system to do so.
AS you indicate while it aint on and I feel for Sony clearly there has been some gaping wholes in their system to cause this and require the downtime and work to fix them.
I will have a guess that the playstation network and SEO service shared the same structure or some code/structure was very similar so that the same exploit could be applied.