Sony's PSN has now been down since the 20th, which is when Sony seemingly noticed a security breach and took down its services. As they've outlined in an FAQ about the attack, they have since brought in some experts to assess the damage, as well as help rebuild the network.
In the interest of not reporting rumors of what exactly happened (Sony is being close-lipped, per usual), I just wanted to give everyone a head's up that if you used a similar password on your PSN account as you did other places, you may wish to change that. Quickly.
14. What personally identifying information do you suspect has been compromised?
Although we are still investigating the details of this incident, we believe that an unauthorized person has obtained the following information provided by PlayStation Network/Qriocity account holders: name, address (city, state, zip), country, email address, birth date, PlayStation Network/Qriocity password, login, and handle/PSN online ID. Other profile data may also have been obtained, including purchase history and billing address (city, state, zip). If an account holder has authorized a sub-account for a dependent, the same data with respect to that dependent may have been obtained. If an account holder provided credit card data through PlayStation Network or Qriocity, it is possible that the credit card number (excluding security code) and expiration date may also have been obtained.
15. How will I know if my personal information has been compromised?
We have provided notices to consumers at the email addresses associated with their PlayStation Network/Qriocity accounts. You may also visit www.us.playstation.com/support and www.qriocity.com for notices regarding this issue. In addition, we have taken steps to disseminate information regarding this issue to media outlets so that consumers are informed. To protect against possible identity theft or other financial loss, we encourage you to remain vigilant to review your credit card account statements and to monitor your credit reports.
There are a lot of maybes, perhaps, and mistakes right now. If you are worried about your credit card information being accessed, I would probably check your bank statements, and/or call your bank and explain to them that your card may have been compromised (via Twitter, I have seen reports of some people mentioning Sony in these calls and receiving a bit more help, but take that with a grain of salt). Also, please do remember to change your passwords every so often, and not reuse them terribly frequently.
Unfortunately, until Sony starts speaking more openly (which they say they won't until they have a better picture), the full extent of the data that may have been compromised cannot be truly assessed.