This will change the default shell for all newly enabled accounts, it will not affect existing enabled shell users.
When enabling a user's shell, three distinct operations are performed. The shell user's password is set to the SiteWorx account password, the user's shell is updated to the default shell setting, and the account is enabled.
A jailed user will have a very limited view of the file system and available Linux commands when logged in.
It is recommended you exercise discretion when giving out shell access, even jailed shell access, to end users in shared hosting environments.