We just reported yesterday that Sony BMG's Greek site had been hacked, and now flaws have been found in the SonyMusic.co.jp site. Just as with the Greek site, the attackers accessed data via a SQL injection flaw.
The attackers appear to be the group known as Lulz Security. That group appears to attack sites mostly for fun or political reasons, not for criminal reasons (although, in reality, it's still criminal behavior).
The attackers stated in a message that "This isn't a 1337 h4x0r, we just want to embarrass Sony some more."
And in yet another hack, a Lebanese hacker group known as "Idahca" used yet another an SQL injection attack to steal data from Sony Ericsson's eShop.
As we noted earlier, Sony has had a nice round bulls-eye on the back of its logo, pasted there since its embarrassing PSN hack, so this might be likely to continue.