I can't say I'm surprised about WordPress, but I am surprised at the amount of websites Drupal and even vBulletin have, I mean I've used those two before, and not to knock them, but I believe WordPress is way above them, although I guess if you want primarily a forum vBulletin might be better than the WordPress forum options, but I don't see why Drupal would have that many, WordPress has so much more to ofter, free or premium.