While Drupal's performance is always of interest, it has a hard time defending itself against the features people want to add. There are different ways to address this, but the "less features" approach is usually not defensible. To defend itself from the feature onslaught, Drupal tries to load as few lines of PHP code as possible, which helps to increase performance. A PHP opcode cache (such as APC) helps even more and points the way...
