Ray Ozzie on nondiscretionary controls:

For years at Lotus, when working on Lotus Notes, customers kept asking for a feature that would enable the sender of an eMail message to “Prevent Copying or Forwarding” of a message. We kept explaining that there was no practical way to implement it. We could block the Print Screen key. We could disable the Forward and Reply and Export and Save As menu items. But because we couldn’t block any programmer from writing a trivial add-in (using the API) to display or extract the email, we resisted implementing the feature for years. Ultimately, we relented due to the combination of competition and customer demand, and the feature exists in the product today.