I would recommend you check your insurance and whether your nice bike is covered when in the cage at work, it's one of the reasons I went to a beater from my Honzo. If there isn't a premium on spots then people can chose to make one nice, but it's a choice and people have the right to park their bike in any free spot unless the owner of the cage says otherwise. Saying you have rights over something because you put some tube around the hook is like me going into a public car park and putting my name on a space, completely meaningless.