"PSN is currently offline, and we are hard at work to resume service," the message reads. "At this time an estimate as to when PSN will be online is unavailable; however, we will update this article as soon as there's additional information." Those affected by the outage are urged to follow the @PlayStation Twitter account for updates on when service has resumed.
Anecdotally, reports we've received suggest that the PSN Store is available to some players, while connecting to an online match results in a server error. Internal testing reveals that Joystiq staffers are unable to connect to Destiny's multiplayer Crucible mode.
Update: As commenter Mule points out, Sony's Twitter suggestion isn't quite accurate. For updates on the status of PSN, follow @AskPlayStation. The @PlayStation account may let you know once the service is back up, but for now is just angry PlayStation owners complaining en masse.
Update 2: PSN is once again online.