By default, shared files and folders will display the list of people with whom the resource is shared.  There is a folder level setting called "Hide Collaborators."  Enabling this setting will:

• Prevent collaborators from seeing the list of other collaborators.
• Prevent collaborators from adding new collaborators.
• Prevent collaborators from assigning tasks to folder co-owners.
• The folder owner and co-owners are still visible.
• The folder owner and co-owners can add new collaborators.

Instructions to enable this setting are available here: Managing Collaborators: Hiding Collaborators