Since the days of CiviCRM as a standalone project are long passed, is there any reason, in 2016, to have a separate database for Drupal and one for CiviCRM? If so, what is the compelling reason? For the record, I only see downsides, not the least of which is backup and restore should disaster strike. I've just taken over the care and feeding of an existing site where separate databases were used in the setup. The customer used the backup_migrate module to do regular database backups and, you guessed it, only the Drupal DB was actually getting backed up.
Thanks for your insight.