I was trying to figure out how to allow someone to edit a page in my personal space. In the permissions tab there were four options: Create, Export, Restrict and Remove. Hmmm, but I just want to allow someone to EDIT an existing page. After a series of trial and error I figured out the "Create" granted Edit permissions on existing pages.

Man, that was a really complicated experience for such a seemingly simple task. I would have saved me 20 minutes if the label had just said "Create / Edit" rather than just "Create." I'd imagine the same goes for other objects like News, Comments and Attachments.