Sony Europe has reset the passwords for a number of PSN users as a "precautionary measure." The only problem is it forgot to tell people it was doing this, leading to panic as many inexplicably were unable to log in to Sony's online service.
After a number of users complained about this on the PlayStation Europe community forums an online support coordinator explained what was going on. "We monitor PSN account[s] for any irregular activity. If such activity is detected we will sometimes reset passwords," the rep explained.
"This was done purely as precautionary measure and there was no specific evidence that any accounts had be compromised," they added. "There is nothing specific to worry about."
The rep noted that "only a small number of users were affected by this," but based on the community thread of over 50 comments, it seems like this was a rather common occurrence. Hopefully next time Sony will tell people when this happens so it doesn't give users a heart attack when they can't access their account and believe it to be hacked.