Official comment
When a user logs in for the first time on a new system, all folders available for syncing in their account are presented in a single dialog. They can be chosen for syncing to that system or not. If admins have made selections of folders to be automatically synced when the userid is created, then those will be checked automatically. After this initial install on a new system, folders are offered to the user via popups whenever the user receives a shared folder from another user. There is no option to automatically accept these to be synced to the system.
Learn more about folder management in Syncplicity here: