What about systems where in order to register you have to type in the difficult-to-automatically-read code - like when you register for yahoo mail, for example.
----- Original Message ----- From: "Mathieu Bouchard" matju@sympatico.ca I say "manually-approved registrations" because automated registrations can be circumvented too easily: just make a bogus account, then login, then cause the same trouble, in very little time.