Over classification is a big problem since it degrades the system, produces unnecessary levels of handling and storage and reinforces silo thinking. It ain't secret just 'cos it's grey.
Eons ago at RAF Stanley we had a very impressive book classified 'SECRET UK EYES A' and 'AIRCREW EYES ONLY'. It contained - amongst other things which were indeed properly classified - a recce guide to Argentinian air assets that still bore the page references of its source. (Date) Flight International (page) along with the suitably exotic red over-stamp top and bottom. I politely asked the owner of the book what was classified about something published in Flight. His reply? "The fact that we are using it!"