Build An Intranet Using Drupal 7

Many developers and organizations have used Drupal to develop corporate websites, news portals, and online communities, but I've yet to see any intranet being built on the Drupal platform.  I'm sure there are intranets out there that were built using Drupal.  They just aren't documented for public viewing or they may be using Open Atrium or Acquia Commons, Drupal installation profiles for intranet or group collaboration.