Having played with this a little now, I think we should go back to Sam's actual designs in terms of permissions and sharing. The screen that lists all added links should have some clarifying text saying something along the lines of "This link will be added to My Library and shared with X, Y and Z. It will be private and will not be findable by anyone else", as well as a change button. When clicking change, the permissions widget should take over the modal.

I think this is better in terms of layering functionality, but also in terms of the available space. When adding 4 links and sharing with 4 people, I can no longer see all of the elements in the type ahead.