Users can have unlimited quota even if the site's Harddisk Quota is limited!!!
Distro: Ubuntu 10.10, ext4 Version: ISPConfig-188.8.131.52.tar.gz
Created a site with quota 50MB and 1 FTP user. But the site owner can create an FTP user with unlimited quota.
Since ISPConfig uses PureFTPD-MySQL, should check the site quota before adding FTP user.
Website quota http://tinypic.com/view.php?pic=2cpyes1&s=7
Reference: http://bugtracker.ispconfig.org/index.php?do=details&task_id=496 "FTP user has nothing to do with FileSystem Quota because an FTP user is a virtual account"
Thanks to all ISPConfig Contributers.