Here is an example situation:

You have a site where your users can register to participate to an event.
You want them to be able to add/invite/subscribe friends of them that are not registered users of your site.
You do not want to allow anonymous users to be able to register to the event. You do want to know who invites who.

One would need to add a permission such as "Can add multiple votes".
The first vote of a registered user would be for himself (with his username).
Then he would be provided with a new blank form where he could enter an arbitrary name (e.g. the name of his/her friend) and make the choices.