This type - a secret private group that you can email to - is great to use as a specific communication channel.
For example, if you employ teens and young adults, you'd be smart as can be creating a private Facebook group for staff. You'd use it to make announcements in addition to your normal means. Tim Jones of Cigana Cafe says this is how his staff work out trading and filling shifts, with immediate results.
It's fabulous for schools or clubs, sporting groups (rowing, hockey, soccer). As a private group only members can see it or post in it. Therefore you can post where the next game will be, who needs and can give rides, and the like. You can also share photos.