Education and "alerts" at various time in the process are part of what we envision. But the cessation of working-as-usual is probably the only thing that may catch some people's attention. Today, it is quite possible that a domain (or aspects of it) can continue working for many weeks after expiration, up until the moment it is deleted or irrevocably purchased or auctioned.
I agree that the domain should stop working, no name service at all, the moment it expires, since that's the most reliable way to get people's attention.
R's, John It is a most effective and tested means. It has worked for utilities companies for years. The customer coming home to find that the power has been turned off quickly gets the customer's attention.
Education? Isn't it obvious, if you don't pay our renewal, your domain will stop working?