Sharing

I am having a difficult time sharing. Where are the boundaries of sharing an object? Does it depend on the amount of attachment you have to that particular thing or is it dependent on need, yours versus theirs? At the group home we try to teach positive sharing and make sure that it does not violate a person's right of ownership.
The DVD's, magazines or other small sundries are something that the gang routinely shares amongst themselves. When does it cross the line, when someone now objects to the sharing? Even sharing amongst the group homes is a touchy subject. We all covet what we are allotted and tend to become defensive when we have to share a resource. You really miss it when it is out of your grasp and notice how much you really depend on it when it is gone.
I know that a resource enhances the quality of life of the people we serve no matter which group home they live in but I want that resource to be on hand for MY people first.