Add a confirmation dialog (with consequences spelled out) when people click on the Share button

More frequently than I would like, our users have confused restrictions with sharing of the page. Their personal spaces are often restricted, then when they add a page they want to share... they "Share" with our entire development group.

This has happened three or four times out of 300 people as they are introduced to the system, and I expect there will be more.

This feature request is to add a confirmation dialog that tells them explicitly that their action will send an email to the users and/or groups selected.