You can view information about server objects in QMC at tab Documents, choose a document, then in the right hand pane Server \ Server Objects.
The Object ID , Type and Owner will be shown.
As an admin you can then delete the object or change ownership.
For more detail control of Server Objects use the QlikView Power Tools.
There are power tools you can use to read the .shared file that will allow you to see, for each user, a wire frame layout of the users sheets and the user objects on those sheets.
There are further power tools that allow you to change server object ownership in batches.
You can even export the contents of the binary.shared file as xml and review the structiure of each user object. Which is very revealing.