Today, I noticed that the document sharing options have changed. The option to manage access used to be in the document context menu, but no it has moved to the details pane ( this thing being the i-icon)

When you click on the Manage Access  link you get another dialog that allows you to stop sharing the document, to grant access or go to the advanced options:

The advanced option is still the same as before, but the big new thing is the Stop sharing. Stop Sharing will removed any guest links and all other users except for you and other owners.

Hmm, I wonder if this is really what you want in a library with certain permissions set. If I offer users a document library with certain permissions would I want them to take permissions away from that default. I can see the potential positives here, but I could also imagine some issues with this empowerment. This option needs a bit more investigation.