The official European PlayStation forums will be undergoing a big change this month. After three days of downtime, starting from March 17th, logging in to the forum will only be possible with a PlayStation Network ID. People who already have a username on the forums will need to link their PSN ID before March 17th or risk starting over with a new account.
The forum will also be updated with various unannounced new features. We hope that these new features are worth the hassle - it seems people aren't very impressed with losing their usernames (which will change to your PSN ID after the switchover). One of the questions on the FAQ hints at future PSN functionality within the forums, but it won't be this month.