I would not prefer to use this method. There is no guarantee that an affected party will notice that an address that they use disappears from DNS. Note that the list of addresses serves both as a registration list and a way to load the DNS zone, and people can be actively using their address without ever using the (public) DNS entry for it. Please understand that there currently is no such thing as "accounts" under which DNS records are registered. The registrations are made by local coordinators (for which there is some information available) on behalf of users who request an allocation. Local coordinators have varying amounts of detail available about the users. There certainly is no list of e-mail addresses of all users available, where they could be contacted about their allocation. Sure it would be nice to move to a new system where more detail is available about every record, like the date of registration and last re-confirmation and a contact address for the user. However, that also has some associated problems (in many countries it is not straightforward to setup such a database, especially not one accessible over internet, while remaining within legal restrictions about storing personal data). It will not be practical to contact everyone and ask them to create some account to manage their allocation. When it is decided to move to such a system, something has to be done about the existing allocations, to the very minimum those addresses that are allocated now should be protected or at least flagged when the new system tries to re-allocate them to someone else. Only unallocated addresses or confirmed obsolete addresses should be re-allocated, and in fact even within the current manual system I almost never re-allocate an abandoned address to someone else. There is no need to do so because of the vast amounts of empty space we have. Rob