Hook Operation FB_OP_PRE_USER not working

I wrote a module that shall set the local drupal username upon registration to the facebook name. I used the fb hook Operation FB_OP_PRE_USER and this code

# Implementation of Hook Facebook
function npfb_fb($op, &$data, $ret) {
  
  if ($op == FB_OP_PRE_USER) {
    $ret['username'] = $ret['info']['name'] . 'blabla';
    $ret['mail'] = 'someone@somewhere.con';   
    
    return $ret;
  }
  
  if ($op == FB_OP_POST_USER) {
        
    npfb_init_fb_user($data[account]); # do various init works
  }
}

The user is created but the username is always blank also I return some value (at least the username should be blabla. The problems seems to be in the function fb_user_create_local_user but I cant figure it out. The username is always blank, I would suggest that the username by default is the facebook real persons name.