OK. Let's say you only want to share users across a multisite installation. In a plain Drupal installation, are these the only tables you need to share? (copied from the single signon module)
* 'default' => 'somesitename_',Anisa.
* 'authmap' => 'shared_',
* 'profile_fields' => 'shared_',
* 'profile_values' => 'shared_',
* 'role' => 'shared_',
* 'sequences' => 'shared_',
* 'sessions' => 'shared_',
* 'users' => 'shared_',
* 'users_roles' => 'shared_',
* 'users_uid_seq' => 'shared_', // for pgsql