The folks at Sony had originally planned the maintenance schedule for PSN to be on last Thursday. However, it was delayed due to some reasons. The new schedule for maintenance was March 4th, on which the network was actually taken down for maintenance.
All the users who were using the network when maintenance started were automatically signed out. According to pre-maintenance announcement, they were not to be able to access any PSN services including PlayStation Store, online play, PlayStation Home, Account Management and official websites associated with the network.