Earlier this week, Sony Europe reset some user's PSN passwords as a "precautionary" measure. Today, Sony America is doing the same thing.
A notice on the official PlayStation forums says that some users "may need to reset" their passwords after Sony detected "irregular activity" on their network.
A Sony rep says:
Note that if you have access to the email address and Date of Birth associated with the account, you will be able to reset it yourself. If you are missing one or both of those, then you will need to contact us for further assistance.
The resets appear to only be affecting a small number of PSN users. Still, it's worth checking that your password still works, and even if it doesn't, it couldn't hurt to change it anyway.
We've contacted Sony for comment, and will update if we hear back.
UPDATE: A Sony spokesperson tells Kotaku:
We routinely monitor for irregular activity, and if such activity is detected, we may sometimes reset passwords of affected SEN accounts as a precautionary measure to protect consumers and their account information.