Add item-level permissions (read access, create and edit accesss) to document libraries
Custom Lists have Item-level permissions for "read access" and "create and edit access" in the advanced permissions (though Users with the "Manage Lists" permission can see and edit everything). That functionality would be very useful in document libraries as well.
Example Scenario #1: A company is reviewing vendors for an upcoming project. All reviews need to be accessible by a manager, but for confidentiality/NDA reasons, the individual reviewers only need to see/edit their own submissions, not their coworkers'.
A library is being used because:
1. lists cannot require attachments (the manager needs the actual word/pdf documents uploaded)
2. reduce confusion for the reviewers (who have varying levels of both general technical experience and familiarity, and little to no SharePoint experience) - adding a list item and remembering to add an attachment might be a bit much for some of them
3. Creating personal default views for each uploader that filter on their own "created by" entries is clunky and infeasible
If the item level permissions were enabled and set to "items that were created by the user", it would handily solve this issue; the manager would have an elevated "Manage Lists" style permission and see everything, but the users would only see their own document uploads.
Example Scenario #2: A director can have one single location to store private (but not confidential) documents for their team members. Team members can only see their own documents (preserving privacy), but the manager can see them all, in one location.
I'm sure there are several other scenarios that could apply
Star D. commented
Also, users could just create their own views without that filter, unless we also created a new permission group and remove the ability to create personal views, then break inheritance on the library and only grant the manager edit/contribute while the other users access through that custom group...which is a little inefficient compared to how nicely item-level permissions address the issue for lists.
Star D. commented
BTW, I realize that in the scenarios I presented you can set the default view to sort on created by and set that to [me] in the default view, but then the manager still has change his or her view from the default to one that isn't.