However, the last thing I want to do is to ban MIME types from
usage. On the contrary; consider my search format, for example. It can
be implemented at once, or once these file formats have standard MIME
types, but at any point, it's easy to add something like
( M =~ video/.* ). That way, it will be optional in the way that it
should be. Those clients that don't have the MIME type attribute
implemented will simply return false on those queries.

Yes.... Vote for Fredrik.... Fredrik President ;)

Eric