There is a scalability issue with the create new wiki page which uses select fields to set the owner and rights. In a very large XEM instance (10000 users) the select list won't be scalable. We need a picker or until we have it we should remove the rights setting feature and the owner setting. Indeed we don't really need this as this can be done later in the wiki.
Alternatively we could have 2 or 3 rights profile (public, protected, private) that set common used rights. This would be even better.