Heads up! Sony is planning some heavy maintenance of the PlayStation Network service this Thursday (January 17). You'll be unable to do practically anything while the engineers tinker with the backend.
From 4pm Thursday 17 January to 4am Friday January 18 GMT, the following services will be kaput during the maintenance: PlayStation Store, Account Management, Account Registration, Transactions via consoles and the sonyentertainmentnetwork.com website.
Although you will still be signed in to PlayStation Network if you manage to do so before the maintenance begins, you still won't be able to access the above features. You might be able to sync your tophies though. Who knows? Give it a go. It'll be a fun experiment.
Sony was found to have sneaked out a patch for its PlayStation Store earlier this week, which fixed a number of issues that users had with the navigation and interface.