Joomla's default database prefix is "jos_" and it can let users change it during installation.
If a user, like me, changed this prefix, users table of Joomla, "jos_users", cannot be synchronized to CiviCRM's contacts databse table.
So in the next version, it is recommended to adapt to non-standard Joomla database prefixes, i.e. prefixes other than "jos_"?
Actually, I do recommend Joomla to have custom user fields, user groups, tags, accessibility control over user groups and tags, so that other addons can do their works based on them and solve many integration problems that go with CiviCRM, SMF, Wordpress....
- Ref. discussion: How to let CiviCRM knows my Joomla database table does not start with"jos_"?