Usually, this is done when the list is to be restricted to a select segment of people. Hidden is usually the right choice. If you will be manually adding people to the list, it would be really nice if you would first create the custom welcome message about the list so folks will know better who, what and why they were signed up for the list. By default a subscriber can remove him or her self from a list by sending a request to listproc. When someone tries to send mail to the list, the mail is sent to the editors.
Most lists only let subscribers post messages.
This prevents some garbage mail, without the work of editing. Listproc can try to remove bad email addresses for you. It misses some, so you may still need to do manual deletes. Auto Delete if possible. Do ALL Deletes manually.