Do not write in this space

Okay, I won't jot down any letters or numbers --- but I WILL make lots of meaningless scribbly lines and ink-smudges in it, so dat YOU can't write anything in dat space, either! PPPPTHTHTHTHPPPPPT!!!

Telling someone "Do not write in this space" on a paperwork-form is virtually a guarantee that he will seethingly scrawl all kinds of infuriated gibberish in that precious little space, especially if he is feeling resentful about having to feverishly fill out the stupid form in the first place ("Whatever happened to the Paperwork-Reduction Act?!"), just as posting a "No Smoking" sign or putting up a "Keep Off The Grass" placard often results in an INCREASE in said unwanted activity, rather than lessening it!