BuddyPress.org

If you are talking about your installation somewhere ,you can easily turn it off (if you are a admin) from the “Buddypress” submenu under the “Site Admin” menu.there is an option “Allow non-friends to post on profile wires:”. you can select “no” for that.

But if you are talking about this buddypress.org site, Andy may think that this feature can be very useful for developers (like us) for contacting each other without having to wait for the invitation accept.

and Don’t forget to turn those Lights OFF.(only if this answers your Question)