I have made nodes where I hid the title and autogenerated it from other metadata: "feedback on $foo by $bar", or "microcontent: site mission", or "%username's personal profile". etceteras. All are unique identifiers, but none are form fields. Most make no sense at all to store in the database either, because all of these can be build on _view or on _load perfectly fine.
I've written a small module, which automatically generates a title: http://drupal.org/project/auto_nodetitle
Concluding: Titles should be optional at all costs. Titles do not need to be stored in the database as single entity. Unique identifier (wich may be represented in $node->title, if that makes backwards compatibility simpler) is required.
I agree that storing titles in the database isn't necessary. Just have the possibilty to define the title per content type (for showing links in the admin interface.). Perhaps a new node hook would do it, so that links to nodes could be generated without doing a full node_load(). -fago