I tried logging in on forums/community sites yesterday and I thought it is possible to do so again. Anyways, there was a security flaw in the log-in system where the hackers (who have obtained our information) has the ability to take over the account. The reason - they have our info. They have our birth dates, full name, and other stuff that could fool the system. Sony has brought PSN back down to prevent this from happening. Sony was given a warning by a security company in regards to this flaw.
Change your email address that is tied with your PSN account and change your passwords directly on your PS3.