Online reports seemingly point out that the PSN password reset system has been compromised.
The system which allows users to reset their passwords only asked for the email address and the users date of birth to reset: obviously this is the same sort of data that the hackers could have stolen from accounts in the first place.
On a positive note users will know if this has happened as they will receive an email about changing password to the registered email address but it does ask the question if Sony had fully thought out the password reset option.