Billing the user department for a new cover (etc.) or for the extra work done (time taken) in removing the graffiti might wake them up a bit! Personally, I have zero tolerance for this sort of abuse. Have they not heard of stickers, tie-on tags, or even surgical tape?
Meanwhile, label remover (available in aerosol form from various sources), plus a bit of elbow grease usually does the trick, depending on the material in question. Trouble is that sometimes the finish ends up being so disfigured that is has to re-painted, or disguised with stickers etc. All a great deal of wasted time due to the thoughtless action of ignorant user staff!
