I’m so glad I found out about this WordPress plugin:

Role Manager:
http://www.im-web-gefunden.de/wordpress-plugins/role-manager/

What does it do? It greatly extends the ability to define what users can do in WordPress, which is great for multi-user blogs.

I’m using it for a client’s site where they want to restrict authors to only be able to edit their own pages (not just posts) and not other’s.

Never before have I wished the author had a donation link on his page