This site is powered by Drupal for Facebook.
The page you see here is also visible in a facebook application.
So currently the title for a user page is [######]@facebook. How can I translate that to their facebook user name only if the account is a facebook account?
Unfortunately there is a limitation in Drupal 6.x, you basically have to hack core to change that.
This new feature just checked in moments ago may solve the problem for you: http://drupal.org/node/612412#comment-3485896