Yikes, first post.
I'm trying to catch up with the thread, but as a bit of potentially useful information, I contacted my CC company customer service yesterday in order to lower the threshold of the SMS warning on CC operations to 50 (it's a very useful service for spotting CC scams and it's generally free on VISA cards).
I stated the reason was that an online service I was using had been potentially compromised. The customer service employee followed the procedure and when we were done, he asked me if this was about "the Sony issue". We discussed a bit and he told me that they had been in fact warned by Sony "prior to the Easter vacations" (which would mean before last Friday) and they had been monitoring operations tied to the Sony websites and cards since then. He in fact stated that all operations tied to Sony websites were blocked at the time.
Take it as you will (I doubt any official statement about being warned by Sony would be given consider the -unlikely- chance of class actions, in order not to join the "you knew and told nothing" bandwagon). This would on one hand confirm that Sony knew well before they told us, but on the other hand, also that they took action immediately to try and prevent any CC scam issue.
I had sent this info to the staff in case it was possibly relevant to the discussion, so ignore the double post in case it was already reported.
Sure it's nice to be able to post finally!