Today between the hourse of 16:00, and 00:00 GMT (12pm to 5pm EST) the PlayStation Network will be largely inaccessible in Europe and North America due to scheduled maintenance.

Sony have take the opportunity to increase the amount of PSP and PlayStation Vita systems that users can tie to their account. Where the previous limit was two, it will now be raised to three.

Users who remain signed in during the downtime should retain access to online gameplay and applications, as well as the PlayStation Store. However Account Management services will not be available.

Source