Look just replace "cancel" with "mark as worthless and sign". Then

No. Replace cancel with 1. Legal wants you to destroy this document 2. The site security officer wants you to destroy the document 3. The license has expired and you must destroy the document and so on. I don't think my life has been all that interesting, but I've had all of those things happen. Of course there is no guarnatee that indiviuals don't have private copies, etc., but you have this situation currently and it works. Replacing cancel with setaside makes Usenet architecture useful for many business semantics/requirements. That's not something I'm willing to trade away and I am surprised that others would... /r$