Peter, get to know Jeff (Toolpants) a little more and you'll see he's got thousands of pictures to add punch to his twisted sense of humor...
You're absolutely right though... carefully removing the black ones will indeed give you something to use when and if the pretty ones are stolen... which seems to happen all the time. I saw a boxster at the post office last week where the center caps had been heisted as well as the pretty chromed air nozzle thingys <--highly technical name!